Reduced environmental hazard leclanche cell having improved performance

ABSTRACT

A low iron zinc anode for a LeClanche cell, and methods of making and using same, are provided for in the invention. The zinc anode contains at least 95% zinc and no more than about 12 ppm iron, and may be configured for use in round or flat LeClanche cells. The zinc anodes of the invention may be used in general purpose and heavy duty batteries containing an electrolyte comprising zinc chloride as a primary component. Cells made in accordance with the invention exhibit improved capacity and other performance characteristics in respect of conventional cells.

This invention was made with Government support. The Government hascertain rights in this invention.

This application is a division of application Ser. No. 08/275,019, filedJul. 13, 1994, and pending.

FIELD OF THE INVENTION

This invention relates to acid-type LeClanche primary cells havingmanganese dioxide cathodes, chloride-based electrolytes, and zincanodes. The anode usually forms a container that holds the contents ofthe cell and serves as a negative current collector. A carbon rodusually serves as a positive current collector. The chloride-basedelectrolyte of the cell of the present invention may contain ammoniumchloride. The present invention relates to cells commonly referred to asLeClanche, zinc-carbon, or zinc-chloride cells. Such terms are usedinterchangeably herein, all referring to the same type of cell orbattery having an anode formed from a zinc alloy, manganese dioxide as acathode, and a chloride-based electrolyte. LeClanche cells are sometimesfurther classified as heavy duty or general purpose cells. Generalpurpose cells and heavy duty cells differ primarily in the type ofmanganese dioxide used as the cathode material. General purpose cellscontain a lower grade of manganese dioxide, and may use a greater amountof ammonium chloride in the electrolyte. Heavy duty cells containmanganese dioxide of increased purity, and typically use a higherproportion of zinc chloride in the electrolyte.

BACKGROUND OF THE INVENTION

LeClanche cells have been commercially important for over a century, andin existence for more than 120 years. Within the last twenty years thecommercial importance of LeClanche cells has diminished as a result ofcompetition from alkaline cells, which provide longer life and generallysuperior performance. Alkaline cells cost two to four times more thanLeClanche cells, however. Despite the commercial success and performanceadvantages of alkaline cells, however, LeClanche cells currently commandan 18% share of the U.S. consumer round cell market. In Japan and mostThird World countries LeClanche cells command a larger share of theconsumer round cell market. Thus, LeClanche cells continue to command acommercially important segment of the worldwide consumer battery market,and are likely to do so for the foreseeable future.

Most improvements in the capacity and shelf life of LeClanche cellsoccurred between 1945 and 1965 before alkaline primary cells becamecommercially important. During those years new materials such asbeneficiated manganese dioxide and zinc chloride electrolyte, and newdesigns such as paper lined cells, were introduced. Since 1965, however,few significant improvements in the performance of LeClanche cells havebeen made. Instead, over the past thirty years most changes in thedesign, construction and materials of LeClanche cells have been relatedto attempts to reduce mercury concentrations, corrosion of the zinc cananode, and hydrogen gas evolution.

To understand how LeClanche cell technology has evolved, it is helpfulto review the basic function, components, and structure of such cells.LeClanche cells have a chloride-based electrolyte usually comprising amixture of zinc chloride, water, ammonium chloride, sometimes zincoxide, and optionally other pH-controlling materials or organiccorrosion inhibitors. The cathode of a LeClanche cell typicallycomprises a mixture of manganese dioxide powder or granules, carbon orgraphite particles, and the foregoing electrolyte mixture which at leastpartially wets the cathode mixture. In a LeClanche cell, a carbon rod,or pencil, is typically centrally disposed in a metal containercomprising zinc, wherein the container (or can) functions as an anode, anegative current collector, and as a container in which various otherelements of the cell are disposed. The carbon rod functions as apositive current collector, and is surrounded by the at least partiallywetted cathode mix, which, in turn, engages the inner surface of theseparator along the cathode's outer periphery. The separator is disposedbetween the outer periphery of the wetted cathode mix and the innersurface of the zinc container, or anode. The electrolyte permeates thecathode mix and the separator, and permits ionic transfer to occurbetween the anodic zinc can and the MnO₂ particles contained in thecathode.

Because the pH of a LeClanche cell is acidic, the chloride-basedelectrolyte strongly promotes the parasitic corrosion of zinc at theboundary between the inner surface of the can and the electrolyte. Infact, the zinc anode in a LeClanche cell is typically consumed by suchreactions to such an extent that by the end of the cell's useful storagelife, corrosion is visually apparent and the walls of the can arenoticeably thinner. Such parasitic corrosive reactions not only affectthe structural integrity of the can but, more importantly, often reducesignificantly the capacity (and therefore the performance) of aLeClanche cell when it has been in storage prior to use. The effect ismore pronounced at high temperatures, where even more capacity is lostin storage due to such parasitic corrosion reactions.

The basic reactions governing corrosion of a zinc can in a LeClanchecell are as follows:

    2H.sub.2 O+2e.sup.- →H.sub.2 +2(OH.sup.-)           (eq. 1)

    Zn→Zn.sup.+2 +2e.sup.-                              (eq. 2)

Equation 1 describes the cathodic reduction of water at the innersurface of the zinc can. Equation 2 describes the oxidation of metalliczinc to valence state +2, wherein two electrons are released.

The two reactions are related in that the onset of one reaction inducesthe occurrence of the other, and thus induces the continuation orperpetuation of both reactions. The two interrelated reactions are notdesired because they corrode the zinc can, and because they increase theamount of hydrogen gas present inside the sealed cell.

Equation 1 shows that the zinc metal of the can and water in theelectrolyte of a LeClanche cell typically react to form hydrogen gas,which accumulates inside the cell. Some provision must be made forpermitting the egress of such evolved gas to avoid cell rupture. Ruptureof a LeClanche cell typically involves not only the release of hydrogengas, but also the release of cathode mix containing acidic, corrosiveelectrolyte which can harm the device containing the cell. Carbon rodsused in most LeClanche cells are often slightly porous and permeable,and therefore permit the egress of a nominal amount of evolved hydrogengas from the cell interior. Because such carbon rods are oftenimpregnated with wax and therefore cannot permit the egress ofsubstantial amounts of evolved hydrogen gas, however, some allowancemust typically be made in the design of LeClanche cell seals andcontainers for increased cell internal pressure owing to theaccumulation of hydrogen gas therewithin. But excessive hydrogen gasproduction can lead to seal failure through overpressurization beyondthe gas venting limits of the seal. Venting degrades the seal and allowswater vapor to escape from the cell, resulting in cell dehydration andfailure. Venting also typically permits oxygen to enter the cell, whereit accelerates the aforementioned corrosion reaction at the innersurface of the zinc can by reacting directly with the zinc.

Equation 2 describes the basic corrosion reaction that typically occursin LeClanche cells, wherein the zinc can progressively dissolves orcorrodes, causing the walls of the zinc can to thin. Additionally,premature structural failure of the battery may occur through localizedcorrosion or "pinholing." Excessive corrosion can also cause prematureperformance failure of the battery through loss of ionic transportcontact between the zinc can and the separator.

Corrosion of the zinc can in a LeClanche cell actually results fromthree different reactions:

corrosion of the zinc can occurring during the generation of electricityby the battery;

parasitic corrosion of the zinc can occurring during discharge of thebattery, and

parasitic corrosion of the zinc can occurring when the battery is instorage and is not being discharged.

The first of the foregoing corrosion reactions fulfills the intendedfunction of the battery, e.g. the generation of electricity, and thusshould not be hindered. The second and third of the foregoing corrosionreactions, however, actually reduce the capacity of the battery, andthus should be prevented to the greatest degree possible. Varioussolutions to the gassing and corrosion problems attending LeClanchecells have been sought for decades. The most popular and widely employedsolutions to both problems in LeClanche cells have been to:

add inorganic corrosion inhibitors to the cathode mix;

add organic corrosion inhibitors to the cathode mix, and

make zinc cans from alloys containing a mixture of zinc, lead, cadmium,manganese, or other metals that inhibit parasitic corrosion reactions.

Several prior art disclosures have been made suggesting the foregoingattempts to solve the corrosion and gassing problems characteristic ofLeClanche cells, including:

    ______________________________________                                                            Inventor/Applicant/                                       Country                                                                              Patent Number                                                                              Publisher      Issue Date                                 ______________________________________                                        U.K.   --           Aufenast et al.                                                                              1963                                       U.K.   --           Shreir         1963                                       U.S.A. 3,650,825    Lihl           1972                                       U.S.A. 3,877,993    Davis          1975                                       U.S.A. 3,928,074    Jung et al.    1975                                       U.S.A. 3,970,476    Cerfon         1976                                       U.S.A. --           Linden         1984                                       Japan  --           Miyazaki et al.                                                                              1987                                       Japan  --           Nikkei New     1992                                                           Materials                                                 Belgium                                                                              --           Meeus          1993                                       ______________________________________                                    

In the proceedings of the 3rd International Symposium for Research andDevelopment in Non-Mechanical Electrical Power Sources held atBournemouth, the United Kingdom in October, 1963, subsequently publishedin 1963 by the MacMillan Company of New York in Volume 1 of thecompilation "Batteries," in the article "Gas formation in dry cells,"Aufenast and Muller discuss gas evolution and zinc corrosion inLeClanche cells at pp. 335-355. They disclose that undesired hydrogengas production resulting from corrosion of the zinc can of LeClanchecells depends on the quality of the zinc can, on the composition of theelectrolyte, and on small quantities of impurities. Aufenast and Mullerdisclose experiments wherein zinc strips having varying concentrationsof different metal impurities were submerged in an electrolytecontaining water, ammonium chloride, and zinc chloride. The hydrogen gasdeveloped by each bimetallic couple was then measured over a fixedlength of time. Their discussion on page 340 points out that ferrousiron and zinc produce "moderately active" hydrogen gas evolution, andthat ferric iron shows no hydrogen gas activity at all.

In the foregoing compilation "Batteries," Shreir shows at pp. 195 thatwhen a bimetallic couple of zinc and iron is placed in a solution ofwater and 1% NaCl, significant weight loss, or corrosion, of the zincoccurs, whereas the iron remains essentially uncorroded.

In U.S. Pat. No. 3,650,825 Lihl discloses a method of manufacturing animproved electrical contact by treating a known contact material such assilver or copper with mercury to enhance the electrical conductivity andcontact making properties of the contact.

For many years mercury has remained the most popular and widely used ofthe inorganic corrosion inhibitors despite its relatively high cost.Mercury is, however, highly toxic. Almost all LeClanche cells aretypically disposed of by being thrown away along with ordinary householdgarbage and trash, whereupon they enter the ordinary waste stream. Whileindividual LeClanche cells usually contain only a small amount ofmercury, the cumulative effect of large numbers of mercury-containingLeClanche cells entering the waste stream could cause significantquantities of mercury to be released to the environment.

Because mercury is toxic, numerous other inorganic and organic corrosioninhibitors, including various petroleum-based products, mineral oils,animal oils, chromates, and chromic acids, have been tested or used inLeClanche cells. Most such inhibitors, however, do not permit the totalelimination of mercury from LeClanche cells. Instead, they typicallypermit only a reduced amount of mercury to be used, and do not permitthe total elimination of mercury from LeClanche cells.

In U.S. Pat. No. 3,877,993 Davis discloses a LeClanche cell having anorganic corrosion inhibitor comprising polymerized or copolymerizeddimethyl dially quaternary ammonium salt. Davis' corrosion inhibitordisperses through the cathode mixture via the electrolyte to the innersurface of the zinc can to be deposited on the inner surface of the zinccan anode where it inhibits, to some degree, the aforementionedcorrosion and gassing reactions. Davis' corrosion inhibitor enables theamount of mercury required in a LeClanche cell to be lowered.

In U.S. Pat. No. 3,928,074 Jung et al. disclose a LeClanche cell havinga polyethylene glycol monoalkyl ether (PEL) corrosion inhibitor added tothe ammonium chloride/water electrolyte thereof. The organic PELadditive reduces gassing rates in LeClanche cells having no mercury tolevels commensurate with similarly constructed LeClanche cellscontaining mercury.

In U.S. Pat. No. 3,970,476 Cerfon discloses a LeClanche cell having amixture of electrolyte and an organic ascorbic acid corrosion inhibitor.Cerfon discloses superior high temperature storage characteristicsresulting from the addition of ascorbic acid to the ammoniumchloride/water electrolyte of a LeClanche cell.

Another means of attempting to solve the gassing and corrosion problemsattending LeClanche cells has been to form the zinc cans thereof fromalloys containing a mixture of zinc, lead, and cadmium, wherein theinner wall of the can is coated with an amalgam of mercury. Cadmium istypically included in such zinc can alloys because it aids the zinc canmanufacturing process. Typically, about 0.01% by weight mercury is addedto the electrolyte of the LeClanche cell at the time of cell manufacturein the form of mercurous chloride. After the cell is assembled andclosed, the mercury disperses towards the inner walls of the zinc can toform a protective mercury-zinc amalgam thereon. The mercury-zinc amalgamreduces undesired parasitic corrosion and gas evolution reactions inLeClanche cells.

In the book entitled "Handbook of Batteries and Fuel Cells," publishedin 1984 by McGraw-Hill Publishing Company, Chapter 5 of which is herebyincorporated by reference, at pp. 5-7 Linden discloses LeClanche cellshaving zinc cans containing up to about 3000 ppm cadmium and more than3000 ppm lead. Linden discloses further that lead contributes to theforming qualities of the can, that cadmium makes the zinccorrosion-resistant to ordinary dry cell electrolytes, adds strength tothe can, and is usually present in amounts of up to 1000 ppm. At page5-7 Linden states that:

[M] etallic impurities such as copper, nickel, iron, and cobalt causecorrosive reactions with the zinc and must be avoided. In addition, ironmakes zinc harder and less workable.

In the paper "New alloy composition for zinc can for carbon-zinc drycells," published in 1987 by the JEC Press in vol. 6 of "Progress inBatteries & Solar Cells," which paper is hereby incorporated byreference, at pp. 110-112 Miyazaki et al. disclose LeClanche cellshaving no mercury therein, wherein the zinc can alloy contains a mixtureof zinc, lead, cadmium, indium, and manganese, and wherein zero-mercurycells having zinc cans made of the disclosed alloy exhibit reasonablygood performance characteristics and corrosion resistance in respect ofLeClanche cells containing mercury.

In the paper "Mercury free dry battery materialized in Japan, mercuryfunction substituted by a combination of materials," published in"Nikkei New Materials" in 1992, the reduction of hydrogen gassing ratesthrough the removal of impurities from zinc can anodes in "manganese drybatteries" is disclosed at pp. 1-10.

In the paper entitled "The PMA Alloy," published in 1993 by the JECPress in No. 5 of the "JEC Battery Newsletter," which paper is herebyincorporated by reference, Meeus discloses at pp. 30-43 zinc cans havinglead concentrations as low as 2000 ppm, having no cadmium therein, andmade by extruding zinc cans from calots. At page 33 Meeus discusses thebeneficial effects of having lead concentrations in zinc cans exceeding2000 ppm, wherein such lead concentrations reduce gassing and corrosionrates.

The foregoing means of reducing or eliminating mercury in LeClanchecells through the use of special alloys in the zinc can anode require,however, the presence of significant amounts of lead, cadmium, or both.It is well known that lead and cadmium are toxic metals. The specialzinc can alloys developed to eliminate the use of mercury in LeClanchecells, and known of heretofore, do not contain reduced concentrations ofeither or both of those toxic metals. Some of the foregoing specialalloys even contain elevated concentrations of both toxic metals.

What is needed is a LeClanche cell having reduced mercury, cadmium, orlead concentrations therein.

What is also needed is a LeClanche cell having improved performance,capacity, and storage characteristics.

What is further needed is a LeClanche cell having the two foregoingattributes, but having, in addition, a slightly increased cost, or thesame cost, as prior art LeClanche cells.

It is therefore an object of the present invention to provide aLeClanche cell having superior performance, capacity, and storagecharacteristics.

It is another object of the present invention to provide a LeClanchecell having increased performance at low cost.

It is still another object of the present invention to provide aLeClanche cell that presents a reduced hazard to the environment,wherein the cell may be disposed of in a landfill without presenting anysignificant hazard to human or other forms of life.

It is a further object yet of the present invention to provide aLeClanche cell having reduced or no mercury therein.

It is a still further object yet of the present invention to provide aLeClanche cell having reduced or no cadmium therein.

It is another object of the present invention to provide a LeClanchecell having reduced or no lead therein.

It is another object yet of the present invention to provide a LeClanchecell having reduced gassing rates.

It is still another object of the present invention to provide aLeClanche cell having reduced parasitic corrosion reactions occurring onthe surface of the zinc anode thereof.

It is still another object yet of the present invention to providemethods of making zinc anodes for LeClanche cells, wherein cells so madeexhibit superior performance, capacity, and storage characteristics.

It is a further object of the present invention to provide methods ofmaking zinc anodes for LeClanche cells that present a reduced hazard tothe environment.

It is a further object yet of the present invention to provide methodsof making corrosion-resistant zinc anodes for LeClanche cells.

It is still another object yet of the present invention to providemethods of making zinc anodes that reduce gassing in LeClanche cells.

It is a feature of the present invention to provide a zinc anode for aLeClanche cell.

It is another feature of the present invention to provide a iron zincanode for a LeClanche cell, the anode consisting essentially of a zincalloy containing at least 95% zinc and no more than about 12 ppm iron byweight.

It is another feature yet of the present invention to provide a zincanode for a LeClanche cell, the anode containing low amounts of cadmium.

It is still another feature yet of the present invention to provide azinc anode for a LeClanche cell, the anode containing no more than about30 ppm cadmium by weight.

It is a further feature of the present invention to provide a zinc anodefor LeClanche cell, the anode containing low amounts of lead.

It is a further feature yet of the present invention to provide a zincanode for a LeClanche cell, the anode containing no more than about 800ppm lead by weight.

It is a still further feature yet of the present invention to provide azinc anode for a LeClanche cell, the anode containing, in addition to nomore than about 12 ppm iron by weight, either alone or in combination,no more than about 30 ppm by weight cadmium, and no more than about 800ppm by weight lead.

It is another feature of the present invention to provide a zinc anodein a LeClanche cell, the anode having no amalgam or mercury disposed onthe surface thereof.

It is a further feature of the present invention to provide a LeClanchecell having reduced mercury therein.

It is yet another feature of the present invention to provide aLeClanche cell having no mercury therein.

It is a still further feature yet of the present invention to provide aLeClanche cell, the cathode, the electrolyte, and the anode thereofcontaining, in combination, no more than about 0.01 percent by weightmercury.

It is a further feature of the present invention to provide a LeClanchecell, the cathode, the electrolyte, and the zinc anode thereofcontaining, in combination, no, or substantially no, mercury.

It is a further feature yet of the present invention to provide a zincalloy for forming a zinc anode of a LeClanche cell, the zinc alloycontaining no more than about 12 ppm iron by weight.

It is a still a further feature yet of the present invention to providea method of making a zinc alloy for forming a zinc anode of a LeClanchecell, the method including the steps of selecting zinc as a startingmaterial, and thereafter minimizing contact between the zinc startingmaterial and susceptible iron.

It is an advantage of the present invention that the zinc anode thereofcosts about the same to manufacture as a conventional zinc anode for aLeClanche cell.

SUMMARY OF THE INVENTION

This invention satisfies the above needs. A novel LeClancheelectrochemical cell, zinc anode therefor, zinc alloy from which thezinc anode is made, and methods of making and using same, are providedfor.

Some objects of the present invention are attained in a zinc anodeconfigured for use in a LeClanche cell, the anode consisting essentiallyof a zinc alloy containing at least 95% zinc and no more than about 12ppm iron by weight.

Other objects of the present invention are attained in a zinc anodeconfigured for use in a LeClanche cell, the anode consisting essentiallyof a zinc alloy containing no more than 12 ppm iron by weight and atleast 96% zinc, at least 97% zinc, at least 98% zinc, at least 99% zinc,or at least 99.5% zinc.

Other objects yet of the present invention are attained In a zinc anodeconfigured for use in a LeClanche cell, the anode consisting essentiallyof a zinc alloy containing at least 95% zinc and no more than about 11ppm iron by weight, no more than about 10 ppm iron by weight, no morethan about 8 ppm iron by weight, no more than about 6 ppm iron byweight, no more than about 4 ppm iron by weight, more than 1 ppm iron byweight, more than about 2 ppm iron by weight, between about 2 ppm ironby weight and about 10 ppm iron by weight, no more than about 6000 ppmby weight lead, no more than about 800 ppm by weight lead, no more thanabout 200 ppm cadmium by weight, or no more than about 30 ppm by weightcadmium.

Still other objects yet of the present invention are attained in a zincanode, the anode consisting essentially of a zinc alloy containing atleast 95% zinc and no more than about 12 ppm iron by weight, wherein theanode is configured for use in a round LeClanche cell and forms acylindrical can having a bottom and a sidewall extending upwardlytherefrom, the can having an initially open top end, the anode isconfigured for use in a round LeClanche cell selected from the groupconsisting of AAA, AA, C and D sizes, the anode forms an inner zinc candisposed within an outer can, the inner can being in electrical contacttherewith, the anode is configured for use in a round LeClanche cell andforms a cylindrical sleeve having open top and bottom ends, the sleevebeing disposed within an outer can and in electrical contact therewith,the anode forms a plating disposed on an electrically conductivesurface, or the anode is configured for use in a flat LeClanche cell andforms a rectangular member having substantially flat opposing major topand bottom surfaces.

Further objects of the present invention are attained in a zinc anodeconfigured for use in a LeClanche cell, the anode consisting essentiallyof a zinc alloy containing up to about 12 ppm iron by weight, up to 2000ppm cadmium by weight, up to 6000 ppm lead by weight, up to 100 ppmmagnesium by weight, up to 600 ppm manganese by weight, up to 200 ppmcopper by weight, up to 10 ppm nickel by weight, up to 5 ppm cobalt byweight, up to 1000 ppm thallium by weight, up to 5 ppm by weight of eachof molybdenum, antimony, arsenic, up to 8000 ppm by weight of each ofaluminum, indium, bismuth, and calcium, the balance being zinc.

Still further objects of the present invention are attained in a zincanode configured for use in a LeClanche cell, the anode consistingessentially of a zinc alloy containing up to 2000 ppm cadmium by weight,up to 6000 ppm lead by weight, up to 100 ppm magnesium by weight, up to600 ppm manganese by weight, up to 200 ppm copper by weight, up to 10ppm nickel by weight, up to 5 ppm cobalt by weight, up to 1000 ppmthallium by weight, up to 5 ppm by weight of each of molybdenum,antimony, arsenic, up to 8000 ppm by weight of each of aluminum, indium,bismuth, and calcium, the alloy containing no more than about 11 ppmiron by weight, no more than about 10 ppm iron by weight, no more thanabout 8 ppm iron by weight, no more than about 6 ppm iron by weight, nomore than about 4 ppm iron by weight, more than 1 ppm iron by weight,more than about 2 ppm iron by weight, or between about 2 ppm iron byweight and about 10 ppm iron by weight, wherein the balance of the alloyis zinc.

Still further objects yet of the present invention are attained in azinc anode configured for use in a LeClanche cell, the anode consistingessentially of a zinc alloy containing up to about 12 ppm iron byweight, up to 2000 ppm cadmium by weight, up to 6000 ppm lead by weight,up to 100 ppm magnesium by weight, up to 600 ppm manganese by weight, upto 200 ppm copper by weight, up to 10 ppm nickel by weight, up to 5 ppmcobalt by weight, up to 1000 ppm thallium by weight, up to 5 ppm byweight of each of molybdenum, antimony, arsenic, up to 8000 ppm byweight of each of aluminum, indium, bismuth, and calcium, the balancebeing zinc, wherein the anode forms a cylindrical can having a bottomand a sidewall extending upwardly therefrom, the can having an initiallyopen top end, the anode is a cylindrical can selected from the groupconsisting of AAA, AA, C and D sizes, or the anode is configured for usein a flat LeClanche cell and forms a rectangular member havingsubstantially flat opposing major top and bottom surfaces.

Additional objects of the present invention are attained in a LeClancheelectrochemical cell comprising a zinc anode, the anode consistingessentially of a zinc alloy containing at least 95% zinc and no morethan about 12 ppm iron by weight, a manganese dioxide cathode, anionically permeable separator interposed between the anode and thecathode, an electrolyte comprising zinc chloride as a primary component,the electrolyte at least partially wetting the anode, the cathode, andthe separator, and a current collector electrically connected to thecathode.

Additional objects yet of the present invention are attained in aLeClanche electrochemical cell comprising a zinc anode, the anodeconsisting essentially of a zinc alloy containing no more than about 12ppm iron by weight, a manganese dioxide cathode, an ionically permeableseparator interposed between the anode and the cathode, an electrolytecomprising zinc chloride as a primary component, the electrolyte atleast partially wetting the anode, the cathode, and the separator, and acurrent collector electrically connected to the cathode, wherein thealloy contains at least 96% zinc, at least 97% zinc, at least 98% zinc,at least 99% zinc, or at least 99.5% zinc.

Still additional objects yet of the present invention are attained in aLeClanche electrochemical cell comprising a zinc anode, the anodeconsisting essentially of a zinc alloy containing at least 95% zinc, amanganese dioxide cathode, an ionically permeable separator interposedbetween the anode and the cathode, an electrolyte comprising zincchloride as a primary component, the electrolyte at least partiallywetting the anode, the cathode, and the separator, and a currentcollector electrically connected to the cathode, wherein the alloycontains no more than about 11 ppm iron by weight, no more than about 10ppm iron by weight, no more than about 8 ppm iron by weight, no morethan about 6 ppm iron by weight, no more than about 4 ppm iron byweight, more than 1 ppm iron by weight, more than about 2 ppm iron byweight, or between about 2 ppm iron by weight and about 10 ppm iron byweight.

Yet additional objects of the present invention are attained in aLeClanche electrochemical cell comprising a zinc anode, the anodeconsisting essentially of a zinc alloy containing at least 95% zinc andno more than about 12 ppm iron by weight, a manganese dioxide cathode,an ionically permeable separator interposed between the anode and thecathode, an electrolyte comprising zinc chloride as a primary component,the electrolyte at least partially wetting the anode, the cathode, andthe separator, and a current collector electrically connected to thecathode, wherein the anode forms a cylindrical can having a bottom and asidewall extending upwardly therefrom, the can having an initially opentop end, the anode is configured for use in a round LeClanche cellselected from the group consisting of AAA, AA, C and D sizes, the anodeforms an inner zinc can disposed within an outer can, the inner canbeing in electrical contact therewith, the anode forms a cylindricalsleeve having open top and bottom ends, the sleeve being disposed withinan outer can and in electrical contact therewith, the anode forms aplating disposed on an electrically conductive surface, or the anode isconfigured for use in a flat LeClanche cell and forms a rectangularmember having substantially flat opposing major top and bottom surfaces.

Additional objects still yet of the present invention are attained in aLeClanche electrochemical cell comprising a zinc anode, the anodeconsisting essentially of a zinc alloy containing at least 95% zinc andno more than about 12 ppm iron by weight, a manganese dioxide cathode,an ionically permeable separator interposed between the anode and thecathode, an electrolyte comprising zinc chloride as a primary component,the electrolyte at least partially wetting the anode, the cathode, andthe separator, and a current collector electrically connected to thecathode, wherein the cell contains no more than about 0.01% mercury byweight, or the cell contains substantially no mercury.

Other objects of the present invention are attained in a zinc alloyconsisting essentially of up to about 12 ppm iron by weight, up to 2000ppm cadmium by weight, up to 6000 ppm lead by weight, up to 100 ppmmagnesium by weight, up to 600 ppm manganese by weight, up to 200 ppmcopper by weight, up to 10 ppm nickel by weight, up to 5 ppm cobalt byweight, up to 1000 ppm thallium by weight, up to 5 ppm by weight of eachof molybdenum, antimony, arsenic, up to 8000 ppm by weight of each ofaluminum, indium, bismuth, and calcium, the balance being zinc.

Other objects yet of the present invention are attained in a zinc alloyconsisting essentially of up to about 12 ppm iron by weight, up to 2000ppm cadmium by weight, up to 6000 ppm lead by weight, up to 100 ppmmagnesium by weight, up to 600 ppm manganese by weight, up to 200 ppmcopper by weight, up to 10 ppm nickel by weight, up to 5 ppm cobalt byweight, up to 1000 ppm thallium by weight, up to 5 ppm by weight of eachof molybdenum, antimony, arsenic, up to 8000 ppm by weight of each ofaluminum, indium, bismuth, and calcium, wherein the alloy contains atleast 96% zinc, at least 97% zinc, at least 98% zinc, at least 99% zinc,or at least 99.5% zinc.

Still other objects of the present invention are attained in a zincalloy consisting essentially of up to 2000 ppm cadmium by weight, up to6000 ppm lead by weight, up to 100 ppm magnesium by weight, up to 600ppm manganese by weight, up to 200 ppm copper by weight, up to 10 ppmnickel by weight, up to 5 ppm cobalt by weight, up to 1000 ppm thalliumby weight, up to 5 ppm by weight of each of molybdenum, antimony,arsenic, up to 8000 ppm by weight of each of aluminum, indium, bismuth,and calcium, wherein the alloy contains no more than about 11 ppm ironby weight, no more than about 10 ppm iron by weight, no more than about8 ppm iron by weight, no more than about 6 ppm iron by weight, no morethan about 6 ppm iron by weight, no more than about 4 ppm iron byweight, more than 1 ppm iron by weight, more than about 2 ppm iron byweight, between about 2 ppm iron by weight and about 10 ppm iron byweight, the balance being zinc.

Still other objects yet of the present invention are attained in a zincalloy consisting essentially of no more than about 12 ppm iron byweight, up to 50 ppm cadmium by weight, up to 1000 ppm lead by weight,up to 30 ppm magnesium by weight, up to 300 ppm manganese by weight, upto 50 ppm copper by weight, up to 5 ppm nickel by weight, up to 2 ppmcobalt by weight, up to 50 ppm thallium by weight, up to 2 ppm by weightof each of molybdenum, antimony, arsenic, up to 1000 ppm by weight ofeach of aluminum, indium, bismuth, and calcium, the balance being zinc.

Still more objects yet of the present invention are attained in a zincalloy consisting essentially of no more than about 12 ppm iron byweight, up to 30 ppm cadmium by weight, up to 800 ppm lead by weight, upto 15 ppm magnesium by weight, up to 150 ppm manganese by weight, up to5 ppm copper by weight, up to 1 ppm nickel by weight, up to 1 ppm cobaltby weight, up to 30 ppm thallium by weight, up to 1 ppm by weight ofeach of molybdenum, antimony, arsenic, up to 500 ppm by weight of eachof aluminum, indium, bismuth, and calcium, the balance being zinc.

Further objects of the present invention are attained in a method ofmaking a zinc anode configured for use in a LeClanche cell, the methodcomprising the steps of selecting as a starting material zinc containingno more than about 12 ppm iron by weight, melting the starting materialto form molten zinc, minimizing contact between the molten zinc andsusceptible iron, adding up to 2000 ppm cadmium by weight, up to 6000ppm lead by weight, up to 100 ppm magnesium by weight, up to 600 ppmmanganese by weight, up to 200 ppm copper by weight, up to 10 ppm nickelby weight, up to 1000 ppm thallium by weight, and up to 8000 ppm byweight of each of aluminum, indium, bismuth, and calcium, to the moltenzinc to form a molten zinc alloy, minimizing contact between the moltenzinc alloy and susceptible iron, cooling the molten zinc alloy to form azinc alloy, and forming the zinc alloy into an anode configured for usein a LeClanche cell, wherein the anode so produced consists essentiallyof a zinc alloy containing at least 95% zinc and no more than about 12ppm iron by weight.

Further objects yet of the present invention are attained in a method ofmaking a zinc anode configured for use in a LeClanche cell, the methodcomprising the steps of selecting as a starting material zinc containingno more than about 12 ppm iron by weight, melting the starting materialto form molten zinc, minimizing contact between the molten zinc andsusceptible iron, adding up to 2000 ppm cadmium by weight, up to 6000ppm lead by weight, up to 100 ppm magnesium by weight, up to 600 ppmmanganese by weight, up to 200 ppm copper by weight, up to 10 ppm nickelby weight, up to 1000 ppm thallium by weight, and up to 8000 ppm byweight of each of aluminum, indium, bismuth, and calcium, to the moltenzinc to form a molten zinc alloy, minimizing contact between the moltenzinc alloy and susceptible iron, cooling the molten zinc alloy to form azinc alloy, forming the zinc alloy into an anode configured for use in aLeClanche cell, and controlling the iron content in the molten zinc, themolten zinc alloy, the zinc alloy, and the anode such that the anodecontains no more than 11 ppm iron by weight, no more than 10 ppm iron byweight, no more than 8 ppm iron by weight, no more than 6 ppm iron byweight, no more than 4 ppm iron by weight, more than 1 ppm iron byweight, more than about 2 ppm iron by weight, or between about 2 ppmiron by weight and 10 ppm iron by weight, wherein the anode so producedcontains at least 95% zinc.

Still further objects yet of the present invention are attained in amethod of making a zinc anode configured for use in a LeClanche cell,the method comprising the steps of selecting as a starting material zinccontaining no more than about 12 ppm iron by weight, melting thestarting material to form molten zinc, minimizing contact between themolten zinc and susceptible iron, adding up to 2000 ppm cadmium byweight, up to 6000 ppm lead by weight, up to 100 ppm magnesium byweight, up to 600 ppm manganese by weight, up to 200 ppm copper byweight, up to 10 ppm nickel by weight, up to 1000 ppm thallium byweight, and up to 8000 ppm by weight of each of aluminum, indium,bismuth, and calcium, to the molten zinc to form a molten zinc alloy,minimizing contact between the molten zinc alloy and susceptible iron,cooling the molten zinc alloy to form a zinc alloy, and forming the zincalloy into an anode configured for use in a LeClanche cell by one of thesteps of deep drawing and impact extruding, wherein the anode soproduced consists essentially of a zinc alloy containing at least 95%zinc and no more than about 12 ppm iron by weight.

Other objects of the present invention are attained in a method ofmaking a zinc anode configured for use in a LeClanche cell, the methodcomprising the steps of selecting as a starting material zinc containingno more than about 12 ppm iron by weight, melting the starting materialto form molten zinc, minimizing contact between the molten zinc andsusceptible iron, adding up to 2000 ppm cadmium by weight, up to 6000ppm lead by weight, up to 100 ppm magnesium by weight, up to 600 ppmmanganese by weight, up to 200 ppm copper by weight, up to 10 ppm nickelby weight, up to 1000 ppm thallium by weight, and up to 8000 ppm byweight of each of aluminum, indium, bismuth, and calcium, to the moltenzinc to form a molten zinc alloy, minimizing contact between the moltenzinc alloy and susceptible iron, cooling the molten zinc alloy to form azinc alloy, and forming the zinc alloy into an anode configured for usein a LeClanche cell such that the anode forms a cylindrical can having abottom and a sidewall extending upwardly therefrom, the can having aninitially open top end, a round LeClanche cell selected from the groupconsisting of AAA, AA, C and D sizes, or a rectangular member havingsubstantially flat opposing major top and bottom surfaces, wherein theanode consists essentially of a zinc alloy containing at least 95% zincand no more than about 12 ppm iron by weight.

Additional objects of the present invention are attained in a method ofmaking an electrochemical LeClanche cell comprising the steps ofselecting a cathode material comprising manganese dioxide, selecting anelectrolyte comprising chloride as a primary component, selecting a zincanode configured for use in the cell, the anode consisting essentiallyof a zinc alloy containing at least 95% zinc and no more than about 12ppm iron by weight, selecting a cathode current collector comprisingcarbonaceous material, selecting an ionically permeable separator havingfirst and second major opposing surfaces, placing the first surface ofthe separator propinquant to the anode, placing the cathode materialpropinquant to the second surface of separator, placing the cathodecurrent collector propinquant to the cathode material, wetting at leastone of the anode, the separator and the cathode material with theelectrolyte, and sealing the cell to at least inhibit the ingress of airtherein.

Additional objects yet of the present invention are attained in a methodof making an electrochemical LeClanche cell comprising the steps ofselecting a cathode material comprising manganese dioxide, selecting anelectrolyte comprising chloride as a primary component, selecting a zincanode configured for use in the cell, the anode consisting essentiallyof a zinc alloy containing no more than about 12 ppm iron by weight andat least 95% zinc, at least 96% zinc, at least 97% zinc, at least 98%zinc, at least 99% zinc, or at least 99.5% zinc, selecting a cathodecurrent collector comprising carbonaceous material, selecting anionically permeable separator having first and second major opposingsurfaces, placing the first surface of the separator propinquant to theanode, placing the cathode material propinquant to the second surface ofseparator, placing the cathode current collector propinquant to thecathode material, wetting at least one of the anode, the separator andthe cathode material with the electrolyte, and sealing the cell to atleast inhibit the ingress of air therein.

Still additional objects of the present invention are attained in amethod of making an electrochemical LeClanche cell comprising the stepsof selecting a cathode material comprising manganese dioxide, selectingan electrolyte comprising chloride as a primary component, selecting azinc anode configured for use in the cell, the anode consistingessentially of a zinc alloy containing at least 95% zinc and no morethan about 11 ppm iron by weight, no more than about 10 ppm iron byweight, no more than about 8 ppm iron by weight, no more than about 6ppm iron by weight, no more than about 4 ppm iron by weight, more than 1ppm iron by weight, more than about 2 ppm iron by weight, or betweenabout 2 ppm iron by weight and about 10 ppm iron by weight, selecting acathode current collector comprising carbonaceous material, selecting anionically permeable separator having first and second major opposingsurfaces, placing the first surface of the separator propinquant to theanode, placing the cathode material propinquant to the second surface ofseparator, placing the cathode current collector propinquant to thecathode material, wetting at least one of the anode, the separator andthe cathode material with the electrolyte, and sealing the cell to atleast inhibit the ingress of air therein.

Still additional objects yet of the present invention are attained in amethod of using a LeClanche electrochemical cell comprising a zincanode, a positive terminal, and a negative terminal, the zinc anodebeing configured for use in the LeClanche cell, the anode consistingessentially of a zinc alloy containing at least 95% zinc and no morethan about 12 ppm iron by weight, the method comprising the step ofdischarging the cell across its positive and negative terminals.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the presentinvention will become better understood by referring to the followingdescription, appended claims, and accompanying drawings, where:

FIG. 1 is a cross-sectional view of a first embodiment of a roundLeClanche cell of the present invention, wherein the zinc can containsno more than about 12 ppm iron by weight;

FIG. 2 is a cross-sectional view of the zinc can of the round LeClanchecell of FIG. 1 prior to cell assembly, and prior to inward crimping ofthe top edge thereof;

FIG. 3 is a cross-sectional view of a second embodiment of a roundLeClanche cell of the present invention, wherein the inner zinc cancontains no more than about 12 ppm iron by weight;

FIG. 4 is a cross-sectional view of a third embodiment of a roundLeClanche cell of the present invention, wherein the can has a zincplating disposed on the inner sidewall thereof, the plating containingno more than about 12 ppm iron by weight;

FIG. 5 is a perspective view of an embodiment of a flat cell LeClanchebattery of the present invention, wherein the zinc anodes of the unitLeClanche cells thereof contain no more than about 12 ppm iron byweight;

FIG. 6 is an enlarged perspective view of a unit LeClanche cell of theflat cell LeClanche battery of FIG. 5;

FIG. 7 is a graph of zinc can iron concentration versus hydrogen gasvolume data for D-size heavy duty LeClanche cells, including those ofthe present invention;

FIG. 8 is a graph of 2.2 Ohm light industrial flashlight test(hereinafter "LIF test") data obtained with conventional D-size heavyduty LeClanche cells and D-size heavy duty LeClanche cells of thepresent invention;

FIG. 9 is a graph of room temperature flash current test (hereinafter RTflash current test) data obtained with conventional D-size heavy dutyLeClanche cells and D-size heavy duty LeClanche cells of the presentinvention;

FIG. 10 is a graph of high temperature flash current test (hereinafterHT flash current test) data obtained with conventional D-size heavy dutyLeClanche cells and D-size heavy duty LeClanche cells of the presentinvention;

FIG. 11 is a graph of RT flash current test data obtained withconventional D-size general purpose LeClanche cells and D-size generalpurpose LeClanche cells of the present invention;

FIG. 12 is a graph of HT flash current test data obtained withconventional D-size general purpose LeClanche cells and D-size generalpurpose LeClanche cells of the present invention;

FIG. 13 is a graph of 3.9 Ohm LIF test data obtained with conventionalC-size heavy duty LeClanche cells and C-size heavy duty LeClanche cellsof the present invention;

FIG. 14 is a graph of RT flash current test data obtained withconventional C-size heavy duty LeClanche cells and C-size heavy dutyLeClanche cells of the present invention;

FIG. 15 is a graph of HT flash current test data obtained with C-sizeheavy duty LeClanche cells of the present invention;

FIG. 16 is a graph of RT flash current test data obtained with AA-sizeheavy duty LeClanche cells of the present invention;

FIG. 17 is a graph of HT flash current test data obtained with AA-sizeheavy duty LeClanche cells of the present invention;

FIG. 18 is a graph of RT flash current test data obtained with AA-sizegeneral purpose LeClanche cells of the present invention;

FIG. 19 is a graph of HT flash current test data obtained with AA-sizegeneral purpose LeClanche cells of the present invention;

FIG. 20 is a graph of RT flash current test data obtained withconventional general purpose LeClanche 6-Volt lantern batteries andgeneral purpose LeClanche 6-Volt lantern batteries of the presentinvention;

FIG. 21 is a graph of HT flash current test data obtained withconventional general purpose LeClanche 6-Volt lantern batteries andgeneral purpose LeClanche 6-Volt lantern batteries of the presentinvention;

FIG. 22 is a graph of RT flash current test data obtained withconventional heavy duty LeClanche 6-Volt lantern batteries and heavyduty LeClanche 6-Volt lantern batteries of the present invention;

FIG. 23 is a graph of HT flash current test data obtained withconventional heavy duty LeClanche 6-Volt lantern batteries and heavyduty LeClanche 6-Volt lantern batteries of the present invention;

FIG. 24 is a graph of zinc can iron concentration versus cell capacitydata for D-size heavy duty LeClanche cells discharged under 2.2 Ohm LIFconditions, including those of the present invention, and

FIG. 25 is a graph of zinc can iron concentration versus cell capacitydata for D-size heavy duty LeClanche cells discharged under 3.9 Ohm LIFconditions, including those of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While those skilled in the art will recognize that the present inventionis applicable to all types of LeClanche cells, batteries, and anodes,and methods of making and using same, the particular embodiments of theinvention set forth herein relate to round cell and 9-Volt LeClanchecells and batteries.

FIG. 1 is a cross-sectional view of a first embodiment of a roundLeClanche cell of the present invention, wherein zinc anode 12 containsno more than about 12 ppm iron by weight. In round cell 10 of FIG. 1,zinc anode 12 (referred to herein interchangeably as zinc can 12, orzinc container 12) serves as the zinc anode of the LeClanche cell, thecan forming a container having bottom 26, upstanding inner sidewall 32,and upstanding outer sidewall 36 extending upwardly therefrom.

Several components of the round LeClanche cell are disposed within zincanode 12 having an initially open top end 38. Carbon rod 14 in thecenter of the cell functions as the cathode current collector. Cathodematerial 16 is disposed around carbon rod 14. Separator 18 preventsinner sidewalls 32 of zinc can 12 from coming into direct electricalcontact with cathode material 16. Liquid electrolyte 20 is disposedsubstantially evenly throughout cathode material 16.

Expansion void 2, disposed between cathode material 16 and seal washer4, permits the expansion of various cell components and gases to occurtherein as the cell discharges. Seal washer 4 typically comprises waximpregnated paper, and forms a barrier atop which asphalt sealant 6 isdisposed. Optionally, an inner seal of the type disclosed in U.S. Patentapplication Ser. No. 08/236,578 entitled "Electrochemical Cell HavingInner Seal," filed on May 2, 1994, the disclosure of which is herebyincorporated by reference in its entirety, may be disposed between sealwasher 4 and cathode material 16.

Top cover 22 is in electrical contact with carbon rod 14, and serves asthe positive terminal of the cell. Bottom cover 24 is in electricalcontact with bottom 26 of zinc can or container 12, and serves as thenegative terminal of the cell. Outer jacket 28, made of steel, paper,plastic or the like, extends between top cover 22 and bottom cover 24,and engages outer upstanding sidewall 36 of zinc anode 12.

FIG. 2 is a cross-sectional view of the zinc anode of the roundLeClanche cell of FIG. 1, wherein zinc anode 12 is shown as it appearsprior to other cell components being placed therein, and prior to thetop end thereof being crimped inwardly during the cell manufacturing andassembly process. Zinc anode 12 comprises bottom 26, inner sidewall 32,top edge 23, and outer sidewall 36, such components forming a can orcontainer 12 having initially open top end 38. In its typical commercialround cell embodiments, zinc anode 12 is characterized by physicaldimensions length 15, radius 21, outer diameter 17, and sidewallthickness 19, as shown in FIG. 2. Table 1 presents preferredspecifications for those dimensions in round LeClanche cells of thepresent invention selected from the group consisting of AAA. AA, C, andD sizes.

                  TABLE 1                                                         ______________________________________                                        Preferred Dimensions of Zinc Anodes for Round LeClanche                       Cells of the Present Invention                                                                            Corresponding                                               Round Cell Size   Specification                                     Dimension and Type          (inches)                                          ______________________________________                                        Length 15 AA (heavy duty)   1.783 ± 0.002                                            AA (general purpose)                                                                            1.783 ± 0.002                                            C (heavy duty)    1.656 ± 0.016                                            C (general purpose)                                                                             1.656 ± 0.016                                            D (heavy duty industrial)                                                                       2.062 ± 0.016                                            D (heavy duty)    2.062 ± 0.016                                            D (general purpose)                                                                             2.062 ± 0.016                                            D lantern (heavy duty)                                                                          3.406 ± 0.016                                            D lantern (general purpose)                                                                     3.406 ± 0.016                                  Outer Diameter                                                                          AA (heavy duty)   0.515 ± 0.003                                  17        AA (general purpose)                                                                            0.515 ± 0.003                                            C (heavy duty)    0.892 ± 0.003                                            C (general purpose)                                                                             0.892 ± 0.003                                            D (heavy duty industrial)                                                                       1.183 ± 0.003                                            D (heavy duty)    1.183 ± 0.003                                            D (general purpose)                                                                             1.183 ± 0.003                                            D lantern (heavy duty)                                                                          1.245 ± 0.003                                            D lantern (general purpose)                                                                     1.183 ± 0.003                                  Thickness 19                                                                            AA (heavy duty)   0.011 - 0.014                                               AA (general purpose)                                                                            0.011 - 0.014                                               C (heavy duty)    0.014 - 0.017                                               C (general purpose)                                                                             0.013 - 0.015                                               D (heavy duty industrial)                                                                       0.014 - 0.016                                               D (heavy duty)    0.016 - 0.018                                               D (general purpose)                                                                             0.013 - 0.015                                               D lantern (heavy duty)                                                                          0.017 - 0.019                                               D lantern (general purpose)                                                                     0.013 - 0.015                                     Radius 21 AA (heavy duty)   0.047                                                       AA (general purpose)                                                                            0.047                                                       C (heavy duty)    0.063                                                       C (general purpose)                                                                             0.063                                                       D (heavy duty industrial)                                                                       0.063                                                       D (heavy duty)    0.063                                                       D (general purpose)                                                                             0.063                                                       D lantern (heavy duty)                                                                          0.063                                                       D lantern (general purpose)                                                                     0.063                                             ______________________________________                                    

To attain maximum performance and reliability in round LeClanche cellsof the present invention, zinc anode 12 should conform to the followingadditional specifications prior to cell assembly. Referring to FIG. 2,top edge 23 should exhibit thereon substantially no irregularities suchas burrs, rough edges, or slivers. Zinc anode 12 should not exhibit anyblisters, cracks, laminations, wrinkles, or tears, and should not haveany foreign material on the surface thereof such as drawing or cleaningcompound residuum. Sidewalls 32 and 36, and bottom 26, should form acylindrical can 12 having a cross-section that is substantially circularwhen viewed at an angle of 90 degrees in respect of a planeperpendicular to longitudinal axis 25.

Most preferably, the dimensions presented in Table 1 should be confirmedby measuring length 15, outside diameter 17, thickness 19, and radius 21of a representative low zinc anode 12 with a Brown & Sharp No. 225 ballmicrometer and a Mituyo Digimatic 6" caliper, wherein can 12 is slitopen, laid flat, and an average of at least six different micrometerreadings is taken for each of dimensions 15, 17, 19, and 21, the averageof each set of measurements falling within the correspondingspecification given in Table 1.

Zinc anode 12 of FIGS. 1 and 2 is most preferably fabricated inaccordance with the deep drawing method set forth infra, but may also bemade in accordance with the less preferred methods of impact extrusion,or rolling and soldering, also described infra.

FIG. 3 is a cross-sectional view of a second embodiment of a roundLeClanche cell of the present invention, wherein inner zinc can 40contains no more than about 12 ppm iron by weight. In FIG. 3, can 41comprises inner zinc can 40 and outer can 42. Outer can 42 may comprisezinc, steel or any other suitable metal or alloy, or optionally, maycomprise any other suitable electrically conductive material such asplastic or graphite. Inner zinc can 40 physically engages, and is inelectrical contact with, outer can 42, and may form an insert can orsleeve that frictionally or otherwise engages the inner sidewall ofouter can 42. Inner zinc can 40 has a bottom 43, the bottom beingcontiguous at its outer perimeter with inner sidewall 33 of inner zinccan 40. Optionally, inner zinc can 40 may have no bottom 43, but mayform a sleeve or cylinder having open top and bottom ends.

Can 41 of FIG. 3 may be formed by pressing together two metal sheets,most preferably at temperatures or pressures sufficient to cause somebonding or welding together of the metal sheets, wherein a first zincalloy sheet containing no more than about 12 ppm iron subsequently formsinner can 40, and a second metal sheet subsequently forms outer can 42.Can 41 may then be formed by any one of the deep drawing, impactextrusion, or rolling processes discussed below. Alternatively, innerzinc can 40 and outer can 42 may first be formed separately by deepdrawing means, followed by inner zinc can 40 being press fitted intoouter can 42 to form can 41.

FIG. 4 is a cross-sectional view of a third embodiment of a roundLeClanche cell of the present invention, wherein can 44 has zinc plating46, the plating containing no more than about 12 ppm iron by weight, andbeing disposed on the inner sidewall 48 of can 44. In the thirdembodiment, can 44 may comprise zinc or, optionally, may comprise anyother suitable metal or alloy. Zinc plating 46 physically engages, andis in electrical contact with, inner sidewall 48 of can 44.

Zinc plating 46 may be deposited upon inner sidewall 48 of can 44 by anyone of several well known electroplating processes. For example,electro-deposition of the zinc alloy of plating 46 may be obtained in asuitable electrolyte solution, wherein can 44 serves as anelectroplating cathode in such suitable electrolyte solution, and directcurrent is introduced through an electroplating zinc alloy anodecontaining no more than about 12 ppm by weight iron. Zinc plating 46 maybe disposed on any suitable electrically conductive material.

FIG. 5 is a perspective view of a flat cell LeClanche battery 50 of thepresent invention. Flat cell battery 50 has a plurality of unit flatcells 62, one disposed atop the other therewithin, the unit flat cells62 being connected electrically in series to positive contact 52 andnegative contact 54. Connector strip 56 connects negative contact 54 tothe zinc anode of the lowermost of unit flat cells 62, the zinc anodecontaining no more than about 12 ppm iron by weight. Outer jacket 58 iselectrically insulated from the plurality of unit flat cells 62. Waxcoating 60 provides a seal for the battery. Typically, six unit flatcells 62 are connected in series to form a 9-volt battery of the typeshown in FIG. 5.

FIG. 6 is an enlarged perspective view of one of the unit flat cells 62of FIG. 5. Plastic envelope 66 has upper aperture 76, wherein outerperimeter 78 defines the lateral extent of upper aperture 76. Plasticenvelope 66 has a lower aperture disposed on the bottom side thereofhaving the same dimensions as the upper aperture, the outer perimeter ofthe lower aperture being aligned vertically below outer perimeter 78 oftop aperture 76.

Several components of flat unit cell 64 are disposed within plasticenvelope 66, including cathode mix 68, separator 70, and zinc anode 72.Cathode mix 68 comprises manganese dioxide, a carbon binder, and anelectrolyte. Most preferably, cathode mix 68 contains about 0.64% byweight acetylene black compressed by 50%, about 53.32% by weightelectrolytic manganese dioxide, about 1.28% by weight ammonium chloride,about 17.41% by weight zinc chloride solution, and about 25.19% byweight water. The upper surface of cathode mix 68 is exposed throughupper aperture 76 to permit electrical contact of cathode mix 68 withconductive carbon coating 74 of the unit cell immediately adjacentthereabove. Separator 70, typically cereal coated Kraft paper or thelike, is disposed between cathode mix 68 and zinc anode 72.

Zinc anode 72 serves as the anode of the flat unit cell, and forms arectangular member having substantially flat opposing major upper andlower surfaces, wherein the major upper surface contacts separator 70and the major lower surface has conductive carbon coating 74 disposedthereupon. Conductive carbon coating 74 is exposed through the loweraperture to permit the coating to function as a current collector forthe cathode mix of the unit cell disposed immediately therebelow. Zincanode 72 of the present invention contains no more than about 12 ppmiron by weight.

Zinc alloy sheets from which zinc anode 72 is formed may be manufacturedin accordance with the process for making a zinc alloy set forth below.Typically, zinc anode 72 is then stamped, die-cut, or otherwise formedfrom the zinc alloy sheets produced in accordance with the presentinvention.

Mercury is eliminated or substantially reduced from cells, batteries,and zinc anodes of the present invention. Unexpectedly, the presentinvention provides a mercury-free or substantially mercury-freeLeClanche cell or battery having performance, capacity, and storagecharacteristics exceeding or at least matching those of prior artLeClanche cells or batteries containing mercury, and zinc anodestherefor. The present invention also provides a LeClanche cell orbattery having a zinc anode containing substantially reduced amounts, incombination, of lead and cadmium, in respect of prior art LeClanchecells, LeClanche batteries, and zinc anodes therefor.

For many years lead levels of at least about 2000 ppm by weight, andmore commonly levels of at least about 3000 ppm by weight, were believedto be required in zinc cans of LeClanche cells to impart sufficientmalleability and workability to the zinc alloy sheets from whichextruded zinc cans were made. Some workability beyond that provided byconventional zinc was also thought to be required in zinc alloy sheetsfrom which rolled or deep drawn zinc cans were made, wherein lead levelsof between about 500 and 1000 ppm by weight were common in combinationwith between about 1000 ppm and 3000 ppm by weight cadmium.

Reducing iron content in zinc anodes of the present invention to 12 ppmor less by weight appeared to permit a dramatic lowering of thethreshold minimum amount of lead required in the zinc alloy used tomanufacture the zinc anode. Reducing iron content also appeared tomaintain desirable cell performance, capacity, and storagecharacteristics. Surprisingly, it was discovered that the lead contentof the zinc alloy could be reduced to a level below about 800 ppm byweight, or even down to about 20-40 ppm by weight, even when cadmiumconcentrations lower than 30 ppm by weight were present in the alloy.Because it is toxic, the dramatic reduction in lead content in zincanodes afforded by the present invention benefits the environment.

For many years cadmium levels of as low as 300 to 800 ppm by weight, butmore typically between about 1000 ppm by weight and about 3000 ppm byweight were believed to be required in zinc cans of LeClanche cells toimpart sufficient strength and zinc corrosion resistance to the zincalloy sheets from which such cans were made during the processes of deepdrawing, impact extrusion, or rolling.

It was discovered that reducing the iron content of the zinc anode ofthe present invention to 12 ppm or less by weight also appeared topermit a dramatic lowering of the threshold minimum amount of cadmiumrequired to manufacture the zinc alloy from which the zinc anodes of thepresent invention were fabricated. Furthermore, it appeared that thepresent invention permitted desirable cell performance, capacity, andstorage characteristics to be maintained, despite the low cadmiumcontent of the zinc anodes thereof. Surprisingly, it was discovered thatthe cadmium content of the zinc alloy from which zinc anodes werefabricated could be reduced to a level below about 200 ppm by weight, oreven down to less than about 30 ppm by weight. Like lead, cadmium istoxic, and therefore the significant reduction of cadmium content inzinc anodes afforded by the present invention benefits the environment.

It was further discovered that small amounts of magnesium and manganesecould be substituted for cadmium to impart greater strength andcorrosion resistance to the zinc alloy from which zinc anodes of thepresent invention are made. Additionally, it was discovered that traceamounts of nickel, cobalt, molybdenum, antimony, and arsenic in the zincalloy impaired battery performance. Thus, the presence of those metalsin the zinc anodes of the present invention should be minimized. In oneembodiment of the present invention, the zinc alloy of the presentinvention from which the zinc anode of the present invention isfabricated consists essentially of the constituents set forth in Table2, in the amounts shown.

                  TABLE 2                                                         ______________________________________                                        First Embodiment of the Zinc Alloy of the Present Invention                   Zinc Alloy        Constituent Content                                         Constituent       (ppm by weight, n)                                          ______________________________________                                        Iron               0 ≦ n ≦ 8                                    Cadmium            0 ≦ n ≦ 30                                   Lead              600 ≦ n ≦ 800                                 Magnesium          6 ≦ n ≦ 15                                   Manganese          60 ≦ n ≦ 150                                 Copper             0 ≦ n ≦ 5                                    Nickel             0 ≦ n ≦ 0.5                                  Cobalt             0 ≦ n ≦ 0.1                                  Molybdenum         0 ≦ n ≦ 1                                    Antimony           0 ≦ n ≦ 1                                    Arsenic            0 ≦ n ≦ 1                                    Aluminum           0 ≦ n ≦ 1                                    Indium             0 ≦ n ≦ 1                                    Bismuth            0 ≦ n ≦ 1                                    Calcium            0 ≦ n ≦ 1                                    Zinc              Balance                                                     ______________________________________                                    

In a second embodiment of the present invention having broader ranges ofconstituent contents, the zinc alloy of the present invention from whichthe zinc anode of the present invention is fabricated consistsessentially of the constituents set forth in Table 3, in the amountsshown.

                  TABLE 3                                                         ______________________________________                                        Second Embodiment of the Zinc Alloy of the Present Invention                  Zinc Alloy        Constituent Content                                         Constituent       (ppm by weight, n)                                          ______________________________________                                        Iron              0 ≦ n ≦ 12                                    Cadmium           0 ≦ n ≦ 1000                                  Lead              0 ≦ n ≦ 6000                                  Magnesium         0 ≦ n ≦ 100                                   Manganese         0 ≦ n ≦ 600                                   Copper            0 ≦ n ≦ 200                                   Nickel            0 ≦ n ≦ 10                                    Cobalt            0 ≦ n ≦ 5                                     Thallium          0 ≦ n ≦ 1000                                  Molybdenum        0 ≦ n ≦ 5                                     Antimony          0 ≦ n ≦ 5                                     Arsenic           0 ≦ n ≦ 5                                     Aluminum          0 ≦ n ≦ 8000                                  Indium            0 ≦ n ≦ 8000                                  Bismuth           0 ≦ n ≦ 8000                                  Calcium           0 ≦ n ≦ 8000                                  Zinc              Balance                                                     ______________________________________                                    

The process of manufacturing the zinc anode of the present inventioncomprises three basic steps:

melting a zinc alloy starting material having an iron content of no morethan about 12 ppm by weight, and adding desired constituents, if any, tothe resulting melt;

casting and rolling, or otherwise forming, the zinc alloy produced in ofthe first step into a zinc alloy calot or sheet, and

fabricating the zinc anode of the present invention from the zinc alloycalot or sheet produced in the second step.

In the first step, the starting material is melted in a suitablecontainer having a refractory or other liner that does not permitsusceptible iron to contact, or migrate into, the melt. The pot needs toreach temperatures sufficient to melt the starting material and anyadditional constituents of the zinc alloy, and thus may be set in afurnace. The furnace may be of the reverberatory type fired by gas oroil. Alternatively, a low frequency or high frequency induction furnacemay be used. As required, constituents other than zinc may be added tothe furnace for incorporation into the melt. If the heating method useddoes not agitate the melt by convection current or other meanssufficiently to ensure even distribution of the added constituentsthroughout the melt, the melt should be stirred or agitated to effecteven distribution. The furnace should hold the zinc alloy melt at atemperature between about 830° and 950° F., depending on metal analysisand casting requirements.

It was determined that contamination of the zinc alloy by iron occurredalmost entirely during the first step when the alloy is molten. Thus,successful practice of the present invention seems to require closeattention to the first step because performance, capacity, and storagecharacteristics of cells and batteries of the present invention improvemarkedly, and in direct relation to the amount by which the iron contentof the zinc anode thereof is reduced; provided, however, that theresulting zinc anode contains less than about 12 ppm by weight iron.

It was also determined that many types of industrial tools, containers,handling vessels, transport conduits, and the like used in the first andsecond steps contain susceptible iron. While the zinc alloy is in amolten state, steps should be taken to minimize contact between thealloy and any iron that is susceptible to migrating into the melt. Bylimiting contact between the molten zinc alloy and susceptible iron,migration of susceptible iron into the melt is minimized or, even morepreferably, eliminated entirely.

Contact between the molten zinc alloy and susceptible iron may becontrolled by using iron-containing devices that are generally notsusceptible to the migration of iron therefrom into the molten zincalloy, or by providing appropriate coatings or linings oniron-containing devices that would otherwise be susceptible to themigration of iron therefrom into the molten or heated zinc alloy. Forexample, appropriate coatings, linings, and materials for preventing themigration of iron into the molten zinc alloy include, but are notlimited to, graphite, 304 Stainless Steel, and refractory materials.

Upon completion of the first step, the iron content of the zinc alloy isthe same or only slightly elevated in respect of the iron content of thezinc ingots used as the starting material. By preventing contaminationof the molten zinc alloy by susceptible iron, the iron content of thesubsequently fabricated zinc anode is typically no more than about 1 toabout 4 ppm greater than the iron content of the zinc starting material.

Absent measures to separate iron from the zinc alloy during the secondor third steps, the iron content of the fabricated zinc anode cannot beless than the iron content of the starting material. Thus, the ironcontent of the starting material must be controlled in the first step.As a starting material, zinc ingots having an iron content as low asabout 2 ppm by weight are readily and economically obtained.Accordingly, such low iron content in the starting material ispreferred, provided such starting material may be procured at a suitableprice.

In the second step, rolling slabs are cast in either open or closed bookmolds. Open molds generally have fins on the bottom for water cooling,whereas closed molds are air cooled. The casting molds should be linedwith refractory of other materials that do not permit the migration ofsusceptible iron therefrom into the zinc alloy, and should also haveclean, smooth surfaces that allow unrestricted shrinkage of the castslab. The use of mold lubricant should be held to a minimum. Castingtemperatures vary with the type of casting and metal analysis, but thenormal range is from about 830° to about 950° F. Mold temperaturesshould vary between about 175° and 250° F., depending on the type ofmold used and metal analysis requirements. The pouring of slabs in bothopen and closed book molds must be at such a rate as to hold turbulenceto a minimum, and provide an even flow of metal across the bottomsurface of the mold. Slabs cast in open molds must be skimmedimmediately to remove surface oxide. Rolling slabs should be cast fromabout 3/4 to about 4 inches thick. The thickness, and length of theslabs are determined by the gage and size of the finish-rolled sheet orcalot, and the capacity of the rolling equipment used.

Temperatures of rolling slabs delivered to the slab roll should rangebetween about 350° and about 500° F. Reductions on the slab roll shouldstart at about 10 percent and then be increased to about 30 percent asthe rolling progresses. The rate of reduction is controlled by metalanalysis, roll shape, and mill capacity. Next, slab rolled material iscut into pack sheets, which are then finished at starting temperaturesbetween about 350° and 450° F. in the pack-rolling process. Packs arerolled at light pressures, with a corresponding loss in temperature, toproduce zinc alloy sheets or calots. Temperatures of finished packs ofzinc alloy sheets or calots vary between about 175° and 250° F.,depending on final thickness and metal analysis.

More detailed information concerning the first and second steps may befound at pages 523-533 of the book "Zinc--The Metal, Its Alloys andCompounds," by C. W. Mathewson, published by Reinhold Publishing Corp ofNew York in 1959, such pages being hereby incorporated by referenceherein. For more information concerning rolling, see pages 343-360 ofVolume 14 ("Forming and Forging") of the Ninth edition of the "MetalsHandbook," edited by Joseph R. Davis, and published by ASM Internationalof Ohio in 1988, such pages being hereby incorporated by referenceherein.

The most preferred fabricating process, or third step, for manufacturingthe round cells of the present invention is to make zinc cans by deepdrawing means, wherein the zinc alloy sheet produced in the second stepis fed through about eight in-line tool and die stations. At eachstation the zinc alloy sheet is stamped by a tool into a die.Progressing from first station to last, the can is drawn deeper at eachstation as the dies become progressively deeper and the diameter of thezinc can decreases. Upon emerging from final tool and die station thezinc can has been formed. Much more detailed information concerning thepreferred deep drawing process of the third step may be found at pages575-590 of Davis, supra, such pages being hereby incorporated byreference herein.

Another means of making round cell zinc cans of the present invention isto take a zinc alloy calot of circular or octagonal shape and containingno more than about 12 ppm iron by weight, and form therefrom a zinc canby impact extrusion means, otherwise commonly referred to as reverseextrusion. After completing the impact extruding step, excess zincshould be trimmed from the zinc can. Care must be taken in the impactextruding step to form zinc cans having sidewalls of sufficientthickness to form a strong can. More information concerning extrusionmay be found at pages 301-326 of Davis, supra, in the Meeus reference,supra, and at pages 559-560 of Mathewson, supra, such pages being herebyincorporated by reference herein

Yet another, but less preferred, method of making zinc cans of thepresent invention is to cut a rectangular piece of metal from a sheet ofzinc alloy containing no more than about 12 ppm iron by weight, and rollthe piece to form a cylinder of appropriate dimensions. A circular pieceis cut from the zinc alloy sheet of such dimensions as to fit in thebottom of the cylinder. The seam in the sidewall of the cylinder is thensoldered together, and the bottom circular piece is soldered in place.The foregoing steps result in the formation of an upstanding zinc canhaving a closed bottom. This is not the most preferred method of makingzinc cans of the present invention because the solder required to closethe seams of the can usually contains substantial amounts of lead. Asmentioned above, lead is undesirable for environmental reasons. Moreinformation concerning this method of making zinc cans may be found atpages 555-559 of Mathewson, supra, such pages being hereby incorporatedby reference herein.

The further the iron content of the zinc anode is reduced below 12 ppmby weight, the greater becomes the cost of effecting the iron reduction.Thus, some balance should be struck between battery performance and thecost of reducing iron content. It was determined that the cost ofreducing the iron content of the zinc anodes of the present inventionbelow 1 ppm iron by weight seemed to outweigh benefits in cellperformance achieved through so doing; zinc ingots for starting materialhaving an iron content of 1 ppm or less by weight are difficult toobtain and expensive.

To reduce the cost of manufacturing the zinc anode of the presentinvention, the anode should have an iron content of at least about 1.5to 2 ppm by weight. Such iron contents permit some relaxation of thestrict controls that would otherwise be required in the manufacturingprocess, and thus reduce manufacturing costs. In some embodiments theiron content is preferably at least about 4 ppm by weight, or may be aslow as 2 ppm by weight. To the extent the cost of reducing the ironcontent is at least equally offset by improved cell or batteryperformance, capacity, or storage characteristics, however, still loweriron contents are preferred.

In weighing the cost of reducing iron content versus improvementsachieved in cell or battery performance, capacity, or storagecharacteristics, it was determined that the iron content of the zincanodes of the present invention should preferably be no more than about10 or 11 ppm, and most preferably should not exceed about 8 ppm.

All iron, lead, cadmium and other metal constituent contents set forthherein were determined using a combined digestion and graphite furnaceatomic absorption technique (hereinafter referred to as the "DGFAAtechnique"). The DGFAA technique comprised the following steps fordetermining the amount of a given constituent in a zinc can sample.

A Hitachi Model Z-8100 polarized Zeeman atomic absorptionspectrophotometer (hereinafter referred to as a "Z-8100") manufacturedby Hitachi, Ltd. of Tokyo, Japan, was used to measure concentrations ofiron, lead, and cadmium present in zinc can samples. When concentrationsof iron, lead, or cadmium in a sample were expected to exceed about 50ppm, the Z-8100 was used in flame mode. When concentrations of iron,lead, or cadmium in a sample were expected to be less than about 50 ppm,the Z-8100 was used in graphite furnace mode.

Helpful information concerning techniques for measuring ppm of iron,lead, and cadmium in zinc can samples using the Z-8100 may be found atpages 4-29, 4-50, and 4-21, respectively, of the guidebook "GraphiteAtomization Analysis Guide for Polarized Zeeman Atomic AbsorptionSpectrophotometry," Part No. 171-9136 YY-T (HTT-LT), published in 1988by Hitachi, Ltd. in Tokyo, Japan, such pages being hereby incorporatedby reference herein. Other, more general information concerning graphitefurnace atomic absorption spectrometry may be found at pp. 1-106 in"Applications of Zeeman Graphite Furnace Atomic Absorption Spectrometryin the Chemical Laboratory and in Toxicology," edited by C. Minoia andS. Caroil, published by Pergamon Press, Ltd., Headington Hill Hall,Oxford, England in 1992, and hereby incorporated by reference herein.

A one gram sample of a zinc can was digested in a solution of 8milliliters of ultra-pure Fischer trace metal grade nitric acid and 10milliliters of purified water. The purified water was processed in aMilli-Q Water Purification System manufactured by Millipore Corporationlocated in Bedford, Massachusetts, wherein the system produced Type Ireagent grade water. Nitric acid was added to the water in increments oftwo milliliters until the sample was dissolved, the solution being heldin a Teflon digestion vessel. Three such solutions were prepared foreach zinc can sample to be tested. The three samples were placed in anMDS-2000 microwave oven manufactured by CEM Corporation of Matthews,N.C. (hereinafter referred to as an "MDS-2000"), where the solutionswere heated to 200° C. over a 20-minute period, and then held at 200° C.for ten minutes. The MDS-2000 was programmed to operate at 65% ofmaximum power output and a maximum pressure of 170 psi; one of the threesamples' temperature and pressure was monitored during the microwaveheating process. The samples were cooled and transferred to 100milliliter flasks containing water purified by the Milli-Q for furtheranalysis in an atomic absorption spectrophotometer. When iron contentsbelow 50 ppm were measured, each sample underwent five sequential steps,all while the Z-8100 was in graphite furnace mode. Those steps, and thephysical conditions corresponding to each, are set forth in Table 4below.

                                      TABLE 4                                     __________________________________________________________________________    Steps Used to Measure ppm Iron in Zinc Can Samples                                        Starting                                                                             Ending        Carrier                                      Z-8100                                                                              Stop  Temperature                                                                          Temperature                                                                           Duration                                                                            Gas                                          Step  Number                                                                              (deg. °C.)                                                                    (deg. °C.)                                                                     (seconds)                                                                           (ml/min)                                     __________________________________________________________________________    Drying                                                                              1      80     140    20    200                                          Drying                                                                              2      140    140    20    200                                          Ashing                                                                              3     1300   1300    30    200                                          Atomizing                                                                           4     2850   2850     5     30                                          Cleaning                                                                            5     2900   2900    10    200                                          __________________________________________________________________________

The Z-8100 was set at the following instrumentation settings when theiron content of a one gram zinc can sample containing less than about 50ppm of iron was measured: element: Fe; wavelength: 248.3 nm; lampcurrent: 10 mA; slit: 0.2 nm; cuvette: pyro-platform; temperaturecontrol: optical temperature; firings: less than 200; measurement mode:working curve; signal mode: background corrected; calculation: peakarea; slicing height: 10%; replicates: 2 standard, 2 samples; no sampleblank; time constant of 0.2 seconds; linear calibration curve.

When lead contents below 50 ppm were measured, each sample underwentfive sequential steps, all while the Z-8100 was in graphite furnacemode. Those steps, and the physical conditions corresponding to each,are set forth in Table 5 below.

                                      TABLE 5                                     __________________________________________________________________________    Steps Used to Measure ppm Lead in Zinc Can Samples                                        Starting                                                                             Ending        Carrier                                      Z-8100                                                                              Stop  Temperature                                                                          Temperature                                                                           Duration                                                                            Gas                                          Step  Number                                                                              (deg. °C.)                                                                    (deg. °C.)                                                                     (seconds)                                                                           (ml/min)                                     __________________________________________________________________________    Drying                                                                              1      80    140     20    200                                          Drying                                                                              2      140   140     20    200                                          Ashing                                                                              3      550   550     30    200                                          Atomizing                                                                           4     2000   2000     5     30                                          Cleaning                                                                            5     2800   2800    10    200                                          __________________________________________________________________________

The Z-8100 was set at the following instrumentation settings when thelead content of a one gram zinc can sample containing less than about 50ppm lead was measured: element: Pb; wavelength: 283.3 nm; lamp current:6 mA; slit: 1.3 nm; cuvette: pyro-platform; temperature control: opticaltemperature; firings: less than 200; measurement mode: working curve;signal mode: background corrected; calculation: peak area; slicingheight: 10%; replicates: 2 standard, 2 samples; no sample blank; timeconstant of 0.2 seconds; linear calibration curve.

When cadmium contents below 50 ppm were measured, each sample underwentfive steps, all while the Z-8100 was in graphite furnace mode. Thosesteps, and the physical conditions corresponding to each, are set forthin Table 6 below.

                                      TABLE 6                                     __________________________________________________________________________    Steps Used to Measure ppm Cadmium in Zinc Can Samples                                     Starting                                                                             Ending        Carrier                                      Z-8100                                                                              Stop  Temperature                                                                          Temperature                                                                           Duration                                                                            Gas                                          Step  Number                                                                              (deg. °C.)                                                                    (deg. °C.)                                                                     (seconds)                                                                           (ml/min)                                     __________________________________________________________________________    Drying                                                                              1      80     140    20    200                                          Drying                                                                              2      140    140    20    200                                          Ashing                                                                              3     1300   1300    30    200                                          Atomizing                                                                           4     2850   2850     5     30                                          Cleaning                                                                            5     2900   2900    10    200                                          __________________________________________________________________________

The Z-8100 was set at the following instrumentation settings when thecadmium content of a one gram zinc can sample containing less than about50 ppm cadmium was measured: element: Cd; wavelength: 228.8 nm; lampcurrent: 8 mA; slit: 1.3 nm; cuvette: pyro-platform; temperaturecontrol: optical temperature; firings: less than 200; measurement mode:standard additions; signal mode: background corrected; calculation: peakarea; slicing height: 10%; replicates: 2 standard, 2 samples; no sampleblank; time constant of 0.2 seconds; linear calibration curve.

Table 7 shows contents of iron, lead, and cadmium contained in zincsamples provided by the NIST (National Institute of Standards andTechnology). Two contents are given for each element in the NISTsamples: the NIST certified value, and the measured value (e.g., thevalue measured using the DGFAA technique). In parentheses immediatelyfollowing each element listed in Table 5 is the NIST SRM (or, NISTStandard Reference Material) number for the zinc alloy sample on whichmeasurements were performed. Each "measured value" was determined usingthe Z-8100 in graphite furnace mode.

                  TABLE 7                                                         ______________________________________                                        NIST and Measured Iron, Lead, and Cadmium                                     Contents in NIST SRM 728 and 631 Zinc Alloy                                   Samples                                                                                    NIST                                                                          Certified Measured  Percent                                      Element      Value     Value     Error                                        ______________________________________                                        Iron (728)    2.7 ppm   1.7 ppm  37.0%                                        Iron (631)   50 ppm    60 ppm    20.0%                                        Lead (728)   11.1 ppm  10.9 ppm   2.0%                                        Cadmium (728)                                                                               1.1 ppm   1.15 ppm  5.0%                                        ______________________________________                                    

Table 7 shows discrepancies between the iron, lead, and cadmium contentsmeasured using the DGFAA technique and the certified contents providedby the NIST. It was concluded that the DGFAA-derived contents were moreaccurate than those provided by the NIST; the NIST determined iron, leadand cadmium contents of the 621 and 728 SRM zinc alloy samples sometwenty years ago using outdated, and less accurate, polographytechniques.

All zinc alloy and zinc anode constituent contents set forth in thespecification and claims hereof are intended to be determined andinterpreted in accordance with the foregoing experimental methods asthey apply to a given constituent. Thus, for example, the terms "zincanode of the present invention" and "zinc alloy of the presentinvention" as used herein mean that the anode or alloy contains no morethan about 12 ppm iron by weight, as measured using the DGFAA techniquesdescribed herein.

The heavy duty cells of Examples A-C, E-G, and J-L were made using theinternal mix constituents and corresponding amounts shown in Table 8.

                  TABLE 8                                                         ______________________________________                                        Heavy Duty Cell Internal Mix Constituents and Amounts                                            Amount (percent by weight                                  Constituent        of total mix)                                              ______________________________________                                        Acetylene Black, compressed 50%                                                                   8.70%                                                     Electrolytic MnO.sub.2                                                                           49.49%                                                     Ammonium Chloride   1.51%                                                     Zinc Oxide          0.33%                                                     Zinc Chloride Solution                                                                           16.71%                                                     Water (@ 160° F.)                                                                         23.27%                                                     ______________________________________                                    

The general purpose cells of Examples D, H, and I were made using theinternal mix constituents and corresponding amounts shown in Table 9.

                  TABLE 9                                                         ______________________________________                                        Heavy Duty Cell Internal Mix Constituents and Amounts                                            Amount (percent by weight                                  Constituent        of total mix)                                              ______________________________________                                        Acetylene Black, compressed 50%                                                                   8.09%                                                     Natural MnO.sub.2  50.48%                                                     Ammonium Chloride   1.46%                                                     Zinc Chloride Solution                                                                           15.77%                                                     Water (@ 160° F.)                                                                         23.27%                                                     ______________________________________                                    

All heavy duty and general purpose cells of Examples A through L weremade in accordance with the structure shown in FIG. 1. None of the cellscontained mercury. In Examples A through L, all conventional anodes andall zinc anodes of the present invention contained less than 800 ppmlead, less than 7 ppm cadmium, less than 5 ppm copper, less than 0.2 ppmnickel, and less than 0.02 ppm indium.

EXAMPLE A

FIG. 7 shows the results of measurements obtained using a cell dischargehydrogen gas volume measurement apparatus. The apparatus measured thevolume of hydrogen gas generated by discharging Rayovac 6D heavy dutyD-size LeClanche cells having zinc cans of varying iron concentrations,including those of the present invention. All cells were discharged inaccordance with the 2.2 Ohm LIF test conditions and procedures describedin Example B, infra. Using linear regression techniques, a linearequation of the form y=-1.096+0.730 was superimposed on the data pointsshown in FIG. 7. An R² correlation coefficient of 0.94 was obtained forthe fit between the straight line of FIG. 7 and the data points showntherein. FIG. 7 and a high R² correlation coefficient show that a stronglinear relationship exists between LeClanche cell zinc can iron contentand gassing rates.

EXAMPLE B

FIG. 8 shows 2.2 Ohm light industrial flashlight test (hereinafter "2.2Ohm LIF test") results obtained with conventional Rayovac 6D heavy dutyD-size LeClanche cells and Rayovac 6D heavy duty D-size LeClanche cellsof the present invention. The LIF tests of Example B used 12conventional cells having zinc cans containing about 17 ppm iron, and 11cells of the present invention having zinc cans containing about 6.6 ppmiron.

Each tested cell energized an electrical circuit having a 2.2 ohmresistor load placed thereacross, such load simulating a typicalflashlight load. Each circuit had a timed switch means for completingand interrupting the circuit. Using the timed switch means, each circuitwas closed, and the battery was discharged thereacross for 4 minutesduring each of eight consecutive hours every day. Each cell then rested,or was not discharged, for 16 consecutive hours thereafter. This 24-hourcycle was repeated for each cell until the closed circuit voltage of thecell reached 0.9 volts, whereupon the 2.2 ohm LIF test for that cell wasterminated. All 2.2 Ohm LIF tests of Example B were conducted at roomtemperature.

As mentioned, 12 conventional cells and 11 cells of the presentinvention of the present invention were tested in the 2.2 Ohm LIF testsof Example B. Closed circuit voltages across each cell were recorded asa function of time during the tests. The average values of thoserecorded voltages are shown in FIG. 8.

FIG. 8 shows that cells of the present invention did not reach 0.9 voltsuntil after about 600 cumulative minutes of discharge, whereasconventional cells reached 0.9 volts after only about 450 cumulativeminutes of discharge. Moreover, the voltage discharge profile of thecells of the present invention is more even and less jagged than that ofthe conventional cells. FIG. 8 therefore shows the surprising andunexpected result that under 2.2 Ohm LIF conditions D-size heavy dutyLeClanche cells of the present invention lasted about one-third longerthan did conventional cells.

EXAMPLE C

FIGS. 9 and 10 show room temperature flash current test (hereinafter "RTflash current test") and high temperature flash current test(hereinafter "HT flash current test") results obtained with conventionalRayovac 6D heavy duty D-size LeClanche cells and Rayovac 6D heavy dutyD-size LeClanche cells of the present invention. The flash current testsof Example C used 10 conventional cells having zinc cans containingabout 17 ppm iron, and 10 cells of the present invention having zinccans containing about 6.6 ppm iron.

Each cell was placed in storage at room temperature (about 70° F.) forthe RT flash current test, or at high temperature (about 113° F.) forthe HT flash current test, after having been discharged across a 2.2 Ohmload until its closed circuit voltage equaled 1.0 Volt. (At 1.0 Voltsabout one-half of a general purpose or heavy duty cell's service liferemains. ) At one week increments thereafter, each cell was temporarilyremoved from room or high temperature storage conditions, and the flashcurrent it could deliver was measured using an ammeter. No electricalload was placed in series with the cell and the ammeter while the flashcurrent was being measured over a 0.5 second interval. Each cell wasthen returned to storage. One week later the flash current measurementprocess was repeated for each cell.

As mentioned, 10 conventional cells and 10 cells of the presentinvention were tested in the RT and HT flash current tests of Example C.The flash current delivered by each cell was recorded weekly during thetests. The average values of those recorded flash currents are shown inFIGS. 9 and 10.

FIG. 9 shows that after three months at room temperature cells of thepresent invention delivered an average of about 0.7 Amperes more thandid conventional cells. FIG. 10 shows that after three months at hightemperature the cells of the present invention delivered an average ofabout 1.1 Amperes more than did the conventional cells. Thus, FIG. 9shows the surprising and unexpected result that under room temperaturestorage conditions cells of the present invention provided, on average,over 20% more current than conventional cells. FIG. 10 shows asurprising 24% increase in current provided under high temperatureconditions by cells of the present invention in respect of conventionalcells.

EXAMPLE D

FIGS. 11 and 12, respectively, show RT and HT flash current test resultsobtained with conventional Rayovac 2D general purpose D-size LeClanchecells and Rayovac 2D general purpose D-size LeClanche cells of thepresent invention. Example D tests used 10 conventional cells havingzinc cans containing about 31.8 ppm iron, and 10 cells of the presentinvention having zinc cans containing about 6.4 ppm iron.

In Example D tests, all cells were tested in accordance with the RT andHT flash current procedures described above in Example C. Average valuesof the flash currents recorded in the Example D tests are shown in FIGS.11 and 12 for RT and HT storage conditions, respectively.

FIG. 11 shows that after three months at room temperature, cells of thepresent invention delivered an average of about 0.05 Amperes less thandid conventional cells. FIG. 12 shows that after three months at hightemperature cells of the present invention delivered an average of about0.15 Amperes more than did the conventional cells. Thus, FIG. 11 showslittle difference in the current provided by cells of the presentinvention and conventional cells under room temperature storageconditions. FIG. 12 shows a slight increase in the current provided bycells of the present invention in respect of conventional cells underhigh temperature conditions.

EXAMPLE E

FIG. 13 shows 3.9 Ohm LIF test results obtained with conventionalRayovac 4C heavy duty C-size LeClanche cells and Rayovac 4C heavy dutyC-size LeClanche cells of the present invention. The LIF tests ofExample E used 15 conventional cells having zinc cans containing about17 ppm iron, and 15 cells of the present invention having zinc canscontaining about 6.1 ppm iron.

In Example E tests, all cells were tested in accordance with the LIFtest procedures described above in Example B, with the exception thatthe cells of Example E were discharged across a 3.9 Ohm load. FIG. 13shows the average values of voltages recorded in the Example E LIFtests.

FIG. 13 shows that cells of the present invention did not reach 0.9volts until after almost 550 cumulative minutes of discharge, whereasconventional cells reached 0.9 volts after only about 430 cumulativeminutes of discharge. FIG. 13 therefore shows the surprising andunexpected result that under 3.9 Ohm LIF conditions C-size heavy dutyLeClanche cells of the present invention lasted about 28% longer thandid conventional cells.

EXAMPLE F

FIGS. 14 and 15, respectively, show RT and HT flash current test resultsobtained with conventional Rayovac 4C heavy duty C-size LeClanche cellsand Rayovac 4C heavy duty C-size LeClanche cells of the presentinvention. Example F tests used 10 conventional cells having zinc canscontaining about 17 ppm iron, and 10 cells of the present inventionhaving zinc cans containing about 6.1 ppm iron.

In Example F tests, all cells were tested in accordance with the RT andHT flash current procedures described above in Example C. Average valuesof the flash currents measured the Example F tests are shown in FIGS. 14and 15 for RT and HT storage conditions, respectively.

FIG. 14 shows that after three months at room temperature cells of thepresent invention delivered an average of about 0.65 Amperes more thandid conventional cells. FIG. 15 shows that after three months at hightemperature cells of the present invention delivered an average of about0.30 Amperes more than did the conventional cells. Thus, FIG. 14 showsthe surprising and unexpected result that under room temperature storageconditions cells of the present invention provided, on average, over 10%more current than did conventional cells. Even more dramatically, FIG.15 shows a surprising 30% increase in the current provided under hightemperature conditions by cells of the present invention in respect ofconventional cells.

EXAMPLE G

FIGS. 16 and 17, respectively, show RT and HT flash current test resultsobtained with Rayovac 5AA heavy duty AA-size LeClanche cells of thepresent invention. Example G tests used 10 cells having low iron zinccans containing about 11.9 ppm iron, and 10 cells having very low ironzinc cans containing about 5.9 ppm iron.

In Example G tests, all cells were tested in accordance with the RT andHT flash current procedures described above in Example C. Average valuesof the flash currents recorded in Example G tests are shown in FIGS. 16and 17 for RT and HT storage conditions, respectively.

FIG. 16 shows that after three months at room temperature very low ironzinc can cells delivered an average of about 0.25 Amperes more than didlow iron zinc can cells. FIG. 17 shows that after three months at hightemperature very low iron zinc can cells delivered an average of about0.10 Amperes more than did low iron zinc can cells. Thus, FIG. 16 showsthat under room temperature storage conditions very low iron zinc cancells provided, on average, about 22% more current than did low ironzinc can cells. FIG. 17 shows a 7% increase in the current providedunder high temperature conditions by very low iron zinc can cells inrespect of low iron zinc can cells.

EXAMPLE H

FIGS. 18 and 19, respectively, show RT and HT flash current test resultsobtained with Rayovac 7AA general purpose AA-size LeClanche cells of thepresent invention. Example H tests used 10 cells having low iron zinccans containing about 11.9 ppm iron, and 10 cells having very low ironzinc cans containing about 5.9 ppm iron.

In Example H tests, all cells were tested in accordance with the RT andHT flash current procedures described above in Example C. Average valuesof the flash currents recorded in Example H tests are shown in FIGS. 18and 19 for room temperature and high temperature storage conditions,respectively.

FIG. 18 shows that after three months at room temperature very low ironzinc can cells delivered an average of about 0.13 Amperes more than didlow iron zinc can cells. FIG. 19 shows that after three months at hightemperature very low iron zinc can cells delivered an average of about0.10 Amperes more than did low iron zinc can cells. Thus, FIG. 18 showsthat under room temperature storage conditions very low iron zinc cancells provided, on average, about 7% more current than did low iron zinccan cells. FIG. 19 shows a 3% increase in the current provided underhigh temperature conditions by very low iron zinc can cells in respectof low iron zinc can cells.

EXAMPLE I

FIGS. 20 and 21, respectively, show RT and HT flash current test resultsobtained with Rayovac 941 lantern batteries containing either fourconventional general purpose LeClanche cells wired in series, orcontaining four general purpose LeClanche cells of the present inventionwired in series. Example I tests used 10 batteries containing 4conventional LeClanche cells having zinc cans containing about 14.9 ppmiron, and 10 batteries containing 4 LeClanche cells of the presentinvention having zinc cans containing about 6.8 ppm iron.

In Example I tests, all batteries were tested in accordance with the RTand HT flash current procedures described above in Example C. Averagevalues of the flash currents recorded in Example I tests are shown inFIGS. 20 and 21 for room temperature and high temperature storageconditions, respectively.

FIG. 20 shows that after three months at room temperature lanternbatteries containing cells of the present invention delivered an averageof about 0.40 Amperes more than did batteries containing conventionalcells. FIG. 21 shows that after three months at high temperature lanternbatteries of the containing cells of the present invention delivered anaverage of about 0.25 Amperes more than did lantern batteries containingconventional cells. Thus, FIG. 20 shows that after three months ofstorage under room temperature conditions lantern batteries of thepresent invention provided about 7% more current than did conventionallantern batteries. FIG. 21 shows that after three months under hightemperature storage conditions lantern batteries of the presentinvention provided a 12% increase in current in respect of conventionallantern batteries.

EXAMPLE J

FIGS. 22 and 23, respectively, show RT and HT flash current test resultsobtained with Rayovac 944 lantern batteries containing either fourconventional heavy duty LeClanche cells wired in series, or having fourheavy duty LeClanche cells of the present invention wired in series.Example J tests used 10 batteries containing 4 conventional LeClanchecells having zinc cans containing about 14.9 ppm iron, and 10 batteriescontaining 4 LeClanche cells of the present invention having zinc canscontaining about 6.8 ppm iron. to In Example J tests, all batteries weretested in accordance with the RT and HT flash current proceduresdescribed above in Example I. Average values of the flash currentsrecorded in Example J tests are shown in FIGS. 22 and 23 for roomtemperature and high temperature storage conditions, respectively.

FIG. 22 shows that after three months at room temperature lanternbatteries containing cells of the present invention delivered about thesame current as lantern batteries containing conventional cells. FIG. 23shows that after three months at high temperature lantern batteries ofthe present invention delivered an average of about 0.10 Amperes morethan did conventional lantern batteries. Thus, FIGS. 22 and 23 show thatsmall increases in current are provided under room or high temperatureconditions by lantern batteries of the present invention in respect ofconventional lantern batteries.

EXAMPLE K

Table 10 presents 2.2 Ohm LIF test data obtained with Rayovac 6D heavyduty D-size LeClanche cells having zinc cans of varying ironconcentrations, including those of the present invention. The firstcolumn of Table 10 shows the iron concentrations of the zinc cans of thevarious heavy duty cells tested. The second column of Table 10 shows thecell number of each cell tested. As a measure of cell capacity, thethird column of Table 10 shows the total number of minutes required foreach tested cell to discharge to 0.9 Volts.

                  TABLE 10                                                        ______________________________________                                        2.2 Ohm LIF Test Data for Heavy Duty D-Size Cells,                            Cell Capacity versus Zinc Can Iron Content                                                             Cell Capacity                                                                 (cumulative minutes                                  Iron Content             required to discharge                                (ppm iron by weight)                                                                       Cell Number to 0.9V)                                             ______________________________________                                        50.0          1          355                                                                2          356                                                                3          355                                                                4          356                                                                5          356                                                                6          367                                                  34.2          7          388                                                                8          386                                                                9          387                                                               10          387                                                               11          387                                                               12          387                                                               13          356                                                               14          356                                                               15          356                                                               16          356                                                               17          356                                                               18          356                                                  12.5         19          420                                                               20          419                                                               21          419                                                               22          419                                                               23          419                                                               24          419                                                               25          449                                                               26          450                                                               27          449                                                               28          449                                                               29          449                                                               30          450                                                   8.4         31          482                                                               32          454                                                               33          465                                                               34          456                                                               35          452                                                               36          482                                                               37          424                                                               38          452                                                               39          424                                                               40          451                                                               41          451                                                               42          453                                                               43          488                                                               44          513                                                               45          486                                                               46          487                                                               47          513                                                               48          485                                                               49          483                                                               50          481                                                               51          482                                                               52          456                                                               53          483                                                               54          482                                                   2.6         55          581                                                               56          547                                                               57          581                                                               58          581                                                               59          579                                                               60          519                                                  ______________________________________                                    

FIG. 24 is a graph of the average cell capacity versus ironconcentration data presented in Table 10 . In FIG. 24, an exponentialcurve of the following form appears:

    y=A.sub.o +A.sub.1 x+A.sub.x X.sup.2 +A.sub.3 x.sup.3      (eq. 3)

The exponential curve of FIG. 24 was obtained by applying polynomialregression techniques to the data points of Table 10 , wherein A₀=613.7, A₁ =-21.75, A₂ =0.641, and A₃ =-0.006. The correlationcoefficient, R, obtained for the fit between the curve of FIG. 24 andthe data points of Table 10 was 0.952. The square of the correlationcoefficient, R², was 0.91.

At pp. 100-103 in "Applied Statistics and the SAS® ProgrammingLanguage," published in 1991 by Prentice Hall of Englewood Cliffs, N.J.in 1991, Cody and Smith teach that the R-squared value of 0.91 may beinterpreted as the proportion of variance in the capacity of the testedcells that can be explained by the variation of iron content in the samecells. Thus, 91% of the variation in capacity of the cells tested inExample K can be explained by the variation in the iron content of thezinc cans of the tested cells.

Because a high R-squared value of 0.91 corresponds to the fit betweenTable 10 data and the curve shown in FIG. 24, a strong, non-linearcorrelation must exist between iron content and capacity in LeClanchecells of the present invention. The nonlinear, steeply curving characterof the left-hand portion of the curve shown in FIG. 24 exhibits clearlythe unexpected and unpredictable discovery made by the inventors of thepresent invention: A dramatic increase in cell capacity is achieved inLeClanche cells having zinc cans containing less than about 12 ppm ironby weight. FIG. 24 shows that the unexpected increase in capacitybecomes especially pronounced when the iron content of the zinc candrops below about 12 ppm by weight. The inventors, therefore, havediscovered that a heretofore unknown criticality exists in respect ofthe iron content of zinc cans for LeClanche cells and the capacity ofsame.

EXAMPLE L

Table 11 presents 3.9 Ohm LIF test data obtained with Rayovac 6D heavyduty D-size LeClanche cells having zinc cans of varying ironconcentrations, including those of the present invention. The firstcolumn of Table 11 shows the iron concentrations of the zinc cans of thevarious heavy duty cells tested. The second column of Table 11 shows thecell number of each cell tested. As a measure of cell capacity, thethird column of Table 11 shows the total number of minutes required foreach tested cell to discharge to 0.9 Volts.

                  TABLE 11                                                        ______________________________________                                        3.9 Ohm LIF Test Data for Heavy Duty D-Size Cells,                            Cell Capacity versus Zinc Can Iron Content                                                             Cell Capacity                                                                 (cumulative minutes                                  Iron Content             required to discharge                                (ppm iron by weight)                                                                       Cell Number to 0.9V)                                             ______________________________________                                        50.0         61          624                                                               62          558                                                               63          630                                                               64          618                                                               65          570                                                               66          624                                                  34.2         67          738                                                               68          684                                                               69          684                                                               70          684                                                               71          738                                                               72          744                                                               73          780                                                               74          738                                                               75          792                                                               76          756                                                               77          768                                                               78          768                                                  12.5         79          864                                                               80          858                                                               81          864                                                               82          918                                                               83          864                                                               84          1044                                                              85          852                                                               86          876                                                               87          846                                                               88          858                                                               89          858                                                               90          858                                                   8.4         91          1026                                                              92          972                                                               93          904                                                               94          990                                                               95          972                                                               96          1032                                                              97          912                                                               98          924                                                               99          966                                                               100         918                                                               101         918                                                               102         912                                                               103         924                                                               104         888                                                               105         828                                                               106         882                                                               107         834                                                               108         828                                                               109         822                                                               110         882                                                               111         870                                                               112         834                                                               113         882                                                               114         882                                                   2.6         115         1002                                                              116         1008                                                              117         1062                                                              118         954                                                               119         1008                                                              120         1020                                                 ______________________________________                                    

FIG. 25 is a graph of the average cell capacity versus ironconcentration data listed in Table 11 . In FIG. 25 an exponential curveof the form of equation 3 appears. The exponential curve of FIG. 25 wasobtained by applying polynomial regression techniques to the data pointsof Table 11, wherein A₀ =17.50, A₁ =-0.339, A₂ =0.009, and A₃ =-1.075.The correlation coefficient obtained for the fit between the curve ofFIG. 25 and the data points of Table 11 was R=0.909 (or, R² =0.83).

In accordance with the teachings of Cody and Smith, supra, the R-squaredvalue of 0.83 may be interpreted as the proportion of variance in thecapacity of the tested cells that can be explained by the variation ofiron content in the same cells. Thus, 83% of the variation in capacityof the cells tested in Example L can be explained by the variation inthe iron content of the zinc cans of the tested cells.

As in Example K, a high R-squared value of 0.83 corresponds to Table 11data and the curve shown in FIG. 25, thus strengthening substantiallythe conclusion that a strong, non-linear correlation exists between ironcontent and capacity in LeClanche cells. And as in Example K, thenonlinear character of the curve shown in FIG. 25 exhibits theunexpected and unpredictable discovery made by the inventors of thepresent invention, wherein a significant increase in cell capacity isachieved in LeClanche cells having zinc cans containing less than about12 ppm by weight iron. Like FIG. 24, FIG. 25 demonstrates that theunexpected increase in capacity becomes especially pronounced when theiron content of zinc cans drops below about 12 ppm by weight. Table 11data, FIG. 25, and an R-Squared correlation coefficient of 0.83, confirmthe discovery of the heretofore unknown and important criticalityexisting in respect of the iron content of zinc cans for LeClanche cellsand the capacity of same.

Those skilled in the art will now see that certain modifications can bemade to the compositions, apparatus, and methods disclosed herein aspreferred embodiments, without departing from the spirit of the presentinvention. Thus, the spirit and scope of the present invention is notrestricted to what is described above. Within the general framework ofLeClanche cells or batteries of the present invention, and methods ofmaking or using same, a very large number of permutations andcombinations will now be seen to be possible, all of which are withinthe scope of the present invention. For example, the present inventionencompasses within its scope low iron zinc alloys having inert or lowchemical activity constituents incorporated therein that are not recitedherein. Such constituents could include, for example, small ceramicbeads or particles. Likewise, although the specification hereof does notdisclose any details concerning a method of making the alloy or anode ofthe present invention that includes the step of continuous casting, thepresent invention encompasses within its scope such a step.

We claim:
 1. A LeClanche electrochemical cell, comprising:(a) a zincanode, the anode consisting essentially of a zinc alloy containing atleast 95% zinc and no more than about 12 ppm iron by weight, (b) amanganese dioxide cathode; (c) an ionically permeable separatorinterposed between the anode and the cathode; (d) an electrolytecomprising zinc chloride as a primary component, the electrolyte atleast partially wetting the anode, the cathode, and the separator, and(e) a current collector electrically connected to the cathode.
 2. Thecell of claim 1, wherein the alloy contains at least 96% zinc.
 3. Thecell of claim 1, wherein the alloy contains at least 97% zinc.
 4. Thecell of claim 1, wherein the alloy contains at least 98% zinc.
 5. Thecell of claim 1, wherein the alloy contains at least 99% zinc.
 6. Thecell of claim 1, wherein the alloy contains at least 99.5% zinc.
 7. Thecell of claim 1, wherein the alloy contains no more than about 11 ppmiron by weight.
 8. The cell of claim 1, wherein the alloy contains nomore than about 10 ppm iron by weight.
 9. The cell of claim 1, whereinthe alloy contains no more than about 8 ppm iron by weight.
 10. The cellof claim 1, wherein the alloy contains no more than about 6 ppm iron byweight.
 11. The cell of claim 1, wherein the alloy contains no more thanabout 4 ppm iron by weight.
 12. The cell of claim 1, wherein the alloycontains between about 2 ppm iron by weight and about 10 ppm iron byweight.
 13. The cell of claim 1, wherein the anode is configured for usein a round LeClanche cell and forms a cylindrical can having a bottomand a sidewall extending upwardly therefrom, the can having an initiallyopen top end.
 14. The cell of claim 13, wherein the anode is furtherconfigured for use in a round LeClanche cell selected from the groupconsisting of AAA, AA, C and D sizes.
 15. The cell of claim 1, whereinthe anode forms an inner zinc can disposed within an outer can, theinner can being in electrical contact therewith.
 16. The cell of claim1, wherein the anode is suitable for use in a round LeClanche cell andforms a cylindrical sleeve having open top and bottom ends, the sleevebeing disposed within an outer can and in electrical contact therewith.17. The cell of claim 1, wherein the anode forms a plating disposed onan electrically conductive surface.
 18. The cell of claim 17, whereinthe electrically conductive surface is metal.
 19. The cell of claim 1,wherein the anode is configured for use in a flat LeClanche cell andforms a rectangular member having substantially flat opposing major topand bottom surfaces.
 20. The cell of claim 1, wherein the cell containsno more than about 0.01% mercury by weight.
 21. The cell of claim 1,wherein the cell contains substantially no mercury.
 22. A method ofusing a LeClanche electrochemical cell comprising a zinc anode, apositive terminal, and a negative terminal, the zinc anode beingconfigured for use in the LeClanche cell, the anode consistingessentially of a zinc alloy containing at least 95% zinc and no morethan about 12 ppm iron by weight, the method comprising the step ofdischarging the cell across its positive and negative terminals.
 23. Thecell of claim 1, wherein the zinc alloy consists of no more than about12 ppm iron, up to 2000 ppm by weight cadmium, up to 6000 ppm by weightlead, up to 100 ppm by weight magnesium, up to 600 ppm by weightmanganese, up to 200 ppm by weight copper, up to 10 ppm by weightnickel, up to 1000 ppm by weight thallium, up to 8000 ppm by weight ofaluminum, up to 8000 ppm by weight of indium, up to 8000 ppm by weightof bismuth, up to 8000 ppm by weight of calcium, and the balance iszinc.
 24. The cell of claim 23, wherein the zinc alloy contains no morethan about 8 ppm iron.